Tìm x thuộc N biết: a) (x-3):2 = 5^14: 5^12

Tìm x∈N biết:

a) x-3:2=514:512.               b) 30:x-7=1519:1518.      c) x70=x.

d) 2x+13=9.81.                      e) 5x+5x+2=650.                    f) 4x-12=25.9