Bài 3:
a) =12.(13+87) = 12.100 = 1200
b) = 4. (-295 + 95) = 4.(-200) = -800
c) = 67.(12 + 89 - 1)= 67.100 = 6700
d) = 26. (-237 + 137) = 26.(-100)= -2600
Bài 4:
a) \(x= \dfrac{210}{-35} = \dfrac{3.7.2.5}{-7.5} = -3.2=-6\)
b) \(x=\dfrac{42}{-7} = \dfrac{6.7}{-7} = -6\)
c) \(x=\dfrac{180}{-12}=\dfrac{3.3.2.10}{-3.2.2}=\dfrac{3.10}{-2}=\dfrac{-30}{2}=-15\)
d) \(x= (-4).25=(-2.2).5.5=-(2.5.2.5)=-10.10=-100\)