Tìm x, biết: a) x+18=6-2x; b) 17-x=7-6x

tìm x,biết:
a) x+18=6-2x
b) 17-x=7-6x
c) x+15=20-4x
d) 7x-4=20+3x
e) -12+x=5x-20
f) 4x-18=x+27