- 18m + 4 = - 18m + 12 

Add on both sides of the equation 18m

- 18m + 4  18m = - 18m + 12 + 18m

- 18m + 18m + 4 = -18m + 18m + 12

0 + 4 = 0 + 12

4 = 12

'4 = 12' is a contradiction thus the equation: '2(2-9m)=6(2-3m)' has no solutions.