a) 156 - (x + 61) = 82
x + 61 = 156 - 82 = 74
x = 74 - 61 = 13
b) 5(x + 35) = 515
x + 35 = 515 : 5 = 103
x = 103 - 35 = 68
c) x : 5 = x : 6
\(\frac{x}{5}-\frac{x}{6}=0\)
\(\frac{6x-5x}{30}=0\)=> x = 0
d) (x - 42)(x - 21) = 0
=> x - 42 = 0 hoặc x - 21 = 0 => x = 42 hoặc x = 21
e) 124 + (118 - x) = 2
118 - x = 2 - 124 = -122
x = 118 - (- 122) = 240