Răspuns :
x/4= x-120 aducem la acelasi numitor
x=4x-480
x-4x=-480
-3x=-480
3x=480
x=160
x=4x-480
x-4x=-480
-3x=-480
3x=480
x=160
x-120=x/4
x-x/4=120
aducem la acelasi numitor
4x-x=120x4
3x=480
x=480/3
x=160bile
verificare
160/4=160-120
40=40