219 - 7(x+1) = 100
7(x+1) = 119
x + 1 = 17
x = 16
(3x - 6).3 = 34
3x - 6 = 33
3x = 33
x = 11
a) 219 - 7(x + 1) = 100
=> 219 - 7x - 7 = 100
=> -7x = 100 - 219 + 7
=> -7x = -112
=> x = -112 ; (-7) = 16
b) (3x - 6) . 3 = 34
=> 9x - 18 = 34
=> 9x = 34 + 18
=> 9x = 99
=> x = 99 : 9 = 11