Bài 1:Tính a) 4.15+28:7-6 mũ 20:6 mũ 18 b)11 mũ 25:11 mũ 23-3 mũ 5:(1 mũ 20+2 mũ 3)-60

a) 4 . 15 + 28 : 7 – $6^{20}$ : $6^{18}$

= 60 + 4 – $6^{2}$

= 64 – 36

= 28

b)$11^{25}$ : $11^{23}$ – $3^{5}$ : ($1^{20}$ + $2^{3}$) – 60

= $11^{2}$ – $3^{5}$ : (1 + 8) – 60

= 121 – $3^{3}$ . $3^{2}$ : $3^{2}$ – 60

= 121 – 27 – 60

= 34