a,24.(75+25)-386
=24.100-386
=2400-386
=2014
b,24:8-4.9+40
=3-36+40
=7
24 . 75 + 24 . 25 - 386
= 24 . (75 + 25) - 386
= 24 . 100 - 386
= 2400 - 386 = 2014
24 : 23 - 4 . (-3)2 + 40
= 24 : 8 - 4 . 9 + 40
= 3 - 36 + 40 = 7
(x - 15) + 75 = 0
x - 15 = 0-75
x - 15 = -75
x = -75 + 15 = -60
118180 - (32 . 52 - 7 . 23)
= 118180 - ( 9 . 25 - 7 . 8)
= 118180 - (225 - 56)
= 118180 - 169 = 118011
|-324| + (-2018) + (-324)
= 324 + (-2018) + (-324)
= [324 + (-324)] + (-2018)
= 0 + (-2018) = -2018
23 . 7 + 7x = 140
8 . 7 + 7x = 140
56 + 7x = 140
7x = 140 - 56 = 84
x = 84 : 7
x = 12
Theo đề bài ta có:
(x : 3 - 4) . 5 = 15
x : 3 - 4 = 15 : 5
x : 3 -4 = 3
x : 3 = 3 + 4 = 7
=> x = 7 . 3 = 21
Vậy x =21