Tìm x, X- 3/10=7/15÷3/5

x- 3/10=7/15÷3/5
b, 30%x-x+5/6=1/3
c, ×/7=6/21
đ, -5/y=20/28
e, -10/15=x/-9=-8/y=z/-21
f, -5/7=30/-x
Tìm x biết