Question

x = x+3
-- -----
6 5

Answer 1

x/6 = (x+3)/5              (mmc de 5 e 6 = 30 então multiplico todos por 30 ) 

30x/6 = 30(x+3)/5

5x = 6(x+3)

5x = 6x + 18

- 18 = 6x - 5x

x = -18                ok 

Answer 2

x/6 = (x+3)/5
5x = 6.(x+3)
5x = 6x+18
5x-6x = 18
-x = 18 .(-1)
x = -18