120 - ( x + 5 ) : 4 x 10 = 20
120 - ( x + 5 ) : 4 = 20 : 10
120 - ( x + 5 ) : 4 = 2
120 - ( x + 5 ) = 2 x 4
120 - ( x + 5 ) = 8
x + 5 = 120 - 8
x + 5 = 112
x = 112 - 5
x = 107
( x + 5 ) : 4 x 10 = 120 - 20
( x + 5 ) : 4 x 10 = 100
( x + 5 ) : 4 = 100 : 10
( x + 5 ) : 4 = 10
x + 5 = 10 x 4
x + 5 = 40
x = 40 - 5
x = 35
Vậy x là 35
120 - ( x + 5 ) : 4 * 10 = 20
=> ( x + 5 ) : 4 * 10 = 120 - 20
=> ( x + 5 ) : 4 * 10 = 100
=> ( x + 5 ) : 4 = 100 : 10
=> ( x + 5 ) : 4 = 10
=> x + 5 = 10 * 4
=> x + 5 = 40
=> x = 40 - 5
=> x = 35