BÀI 1 :
100+ 430+ 2145-530 = [( 100+430)-530] +2145
= 530-530+2145
= 0 + 2145
= 2145
-12.5=-60
12 .13+13 ,( -22) = 13.( -22+12)
= 13.(-10)
= -130
[ 14 : ( -2) +7] : 2012 = ( -7 +7) : 2012
= 0 : 2012
= 0
BÀI 2
3x - 5 = -7 -13
=> 3x- 5 = -20
=> 3x = -15
=> x = -5
IxI -10 = -3
=> I xI = 13
=> x = \(\pm\)13