Vă rog frumos! Dau coroană

Răspuns:
a)5x-2x=21
x=21/3
x=7
b)7x+x=-48
X=-48/8
x=-6
c)-3x-2x=-30
x=30/5
x=6
d)-x-6x=-56
x=56/7
x=8
e)-x+7x=-42
x=-42/6
x=-7
f)-x-2x=27
x=27/-3
x=-9