Tìm x biết: x/14 = 1/2; x/15 = 4/20; 3*x/20 = 3/4

Tìm x biết:
x/14=1/2
x/15=4/20
3*x/20=3/4.
x+2/14=1/2
x-1/15=4/20
x-7/12=12/16.