Bagaimana caranya 3a+18÷4=10a-2÷3

3a + 18 : 4 = 10a - 2 : 3
9a + 54 = 40a - 8
31a = 62
a= 62/31 = 2

3a + 18 : 4 = 10a - 2 : 3
3a + 18/4 = 10a - 2/3
3a - 10a = -2/3 - 18/4
-7a = -8/12 - 54/12
-7a = -62/12
a = -62/12 : (-7)
a = -62/12 × (-1/7)
a = 62/84
a = 31/42