1) 168 – ( 18 – 2x ) x 12 = 120
2) [ 75 + ( 16 – x ) ] x 2 = 156
3) 124 – 24 x ( 3x – 16 ) = 76
4) [ ( 10 – x ) x 2 + 5 ] : 3 – 2 = 3
5) [ 80 + ( 62 – x ) ] : 17 – 7 = 1
6) 65 – ( 5x – 70 ) : 2 = 50
7) 504 : ( 136 – 2x ) + 4 = 32
8) ( 13x – 28 ) x 15 – 5 x 2 mũ 3 = 320
M.n giúp em vs ạ, em cần gấp lắm lun. Thanks ạ !!!
Giải thích các bước giải:
Ta có:
\(\begin{array}{l}
1,\\
168 – \left( {18 – 2x} \right).12 = 120\\
\Leftrightarrow \left( {18 – 2x} \right).12 = 168 – 120\\
\Leftrightarrow \left( {18 – 2x} \right).12 = 48\\
\Leftrightarrow 18 – 2x = 48:12\\
\Leftrightarrow 18 – 2x = 4\\
\Leftrightarrow 2x = 18 – 4\\
\Leftrightarrow 2x = 14\\
\Leftrightarrow x = 14:2\\
\Leftrightarrow x = 7\\
2,\\
\left[ {75 + \left( {16 – x} \right)} \right].2 = 156\\
\Leftrightarrow 75 + \left( {16 – x} \right) = 156:2\\
\Leftrightarrow 75 + \left( {16 – x} \right) = 78\\
\Leftrightarrow 16 – x = 78 – 75\\
\Leftrightarrow 16 – x = 3\\
\Leftrightarrow x = 16 – 3\\
\Leftrightarrow x = 13\\
3,\\
124 – 24.\left( {3x – 16} \right) = 76\\
\Leftrightarrow 24.\left( {3x – 16} \right) = 124 – 76\\
\Leftrightarrow 24.\left( {3x – 16} \right) = 48\\
\Leftrightarrow 3x – 16 = 48:24\\
\Leftrightarrow 3x – 16 = 2\\
\Leftrightarrow 3x = 16 + 2\\
\Leftrightarrow 3x = 18\\
\Leftrightarrow x = 18:3\\
\Leftrightarrow x = 6\\
4,\\
\left[ {\left( {10 – x} \right).2 + 5} \right]:3 – 2 = 3\\
\Leftrightarrow \left[ {\left( {10 – x} \right).2 + 5} \right]:3 = 3 + 2\\
\Leftrightarrow \left[ {\left( {10 – x} \right).2 + 5} \right]:3 = 5\\
\Leftrightarrow \left( {10 – x} \right).2 + 5 = 3.5\\
\Leftrightarrow \left( {10 – x} \right).2 + 5 = 15\\
\Leftrightarrow \left( {10 – x} \right).2 = 15 – 5\\
\Leftrightarrow \left( {10 – x} \right).2 = 10\\
\Leftrightarrow 10 – x = 10:2\\
\Leftrightarrow 10 – x = 5\\
\Leftrightarrow x = 10 – 5\\
\Leftrightarrow x = 5\\
5,\\
\left[ {80 + \left( {62 – x} \right)} \right]:17 – 7 = 1\\
\Leftrightarrow \left[ {80 + \left( {62 – x} \right)} \right]:17 = 1 + 7\\
\Leftrightarrow \left[ {80 + \left( {62 – x} \right)} \right]:17 = 8\\
\Leftrightarrow 80 + \left( {62 – x} \right) = 17.8\\
\Leftrightarrow 80 + \left( {62 – x} \right) = 136\\
\Leftrightarrow 62 – x = 136 – 80\\
\Leftrightarrow 62 – x = 56\\
\Leftrightarrow x = 62 – 56\\
\Leftrightarrow x = 6\\
6,\\
65 – \left( {5x – 70} \right):2 = 50\\
\Leftrightarrow \left( {5x – 70} \right):2 = 65 – 50\\
\Leftrightarrow \left( {5x – 70} \right):2 = 15\\
\Leftrightarrow 5x – 70 = 15.2\\
\Leftrightarrow 5x – 70 = 30\\
\Leftrightarrow 5x = 30 + 70\\
\Leftrightarrow 5x = 100\\
\Leftrightarrow x = 100:5\\
\Leftrightarrow x = 20\\
7,\\
504:\left( {136 – 2x} \right) + 4 = 32\\
\Leftrightarrow 504:\left( {136 – 2x} \right) = 32 – 4\\
\Leftrightarrow 504:\left( {136 – 2x} \right) = 28\\
\Leftrightarrow 136 – 2x = 504:28\\
\Leftrightarrow 136 – 2x = 18\\
\Leftrightarrow 2x = 136 – 18\\
\Leftrightarrow 2x = 118\\
\Leftrightarrow x = 118:2\\
\Leftrightarrow x = 59
\end{array}\)
\(\begin{array}{l}
8,\\
\left( {13x – 28} \right).15 – {5.2^3} = 320\\
\Leftrightarrow \left( {13x – 28} \right).15 – 5.8 = 320\\
\Leftrightarrow \left( {13x – 28} \right).15 – 40 = 320\\
\Leftrightarrow \left( {13x – 28} \right).15 = 320 + 40\\
\Leftrightarrow \left( {13x – 28} \right).15 = 360\\
\Leftrightarrow 13x – 28 = 360:15\\
\Leftrightarrow 13x – 28 = 24\\
\Leftrightarrow 13x = 28 + 24\\
\Leftrightarrow 13x = 52\\
\Leftrightarrow x = 52:13\\
\Leftrightarrow x = 4
\end{array}\)