1.Tìm x: a) 7,5 × x + x × 3,5=39,93 b) x : 4 + x =3,75

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1. $a) 7,5 × x + x × 3,5 = 39,93$

   $⇒ x × (7,5 + 3,5) = 39,93$

   $⇒ x × 11 = 39,93$

   $⇒ x = 39,93 ÷ 11$

   $⇒ x = 3,63$

   $Vậy$ $x = 3,63$

   $b) x : 4 + x =3,75$

   $⇒ x × \dfrac{1}{4} +x = 3,75$

   $⇒ x × (\dfrac{1}{4} + 1) = 3,75$

   $⇒ x × \dfrac{5}{4} = 3,75$

   $⇒ x = 3,75 ÷ \dfrac{5}{4}$

   $⇒ x = 3$

   $Vậy$ $x = 3$

    

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2. $a) 7,5 × x + x × 3,5=39,93$

   $7,5x + 3,5x = 39,93$

   $(7,5+3,5)x = 39,93$

   $11x = 39,93$

   $x = 3,63$

   $b) x : 4 + x =3,75$

   $1/4x + x=3,75$

   $5/4x=3,75$

   $x=3$

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