Hey there!!
First step is not combine the like terms
7x + 14 - 3x = 30
Like terms = 7x and -3x
Combine them
we get 4x
4x + 14 + 30
Now subtract 14 on both sides
4x +14 - 14 = 30 - 14
4x = 16
Now divide by 4 on both sides
4x / 4 = 16 / 4
x = 4
There we go, the required answer is 4