Lời giải :
Bài 1 :
a,
`56+7.(-5)+(-9).(-2)`
`=56+(-35)+18`
`=56-35+18`
`=39`
b,
`2.(-3)^2+5.(-2)^2`
`=2.9+5.4`
`=18+20`
`=38`
c,
`338.(348-217)-348.(338-217)`
`=338.348-338.217-338.348+348.217`
`=(338.348-338.348)+(348.217-338.217)`
`=217.(348-338)`
`=217.10`
`=2170`
d,
`|27|+(-6).[(-3).(-2)+23.42]`
`=27+(-6).(6+966)`
`=27+(-6).972`
`=27+(-5832)`
`=27-5832`
`=-5805`
Bài 2 :
a,
`-x+7=-5`
`->-x=-5-7`
`->-x=-12`
`->x=12` ( tm )
Vậy `x=12`
