Start first with the coefficient of x, which will be 1/4 as you want to find 1/4 of x. Now, minus 3 to that to give you 3 fewer than 1/4x. You know this equates to 12, so your expression is:
1/4x - 3 = 12
Or you can write it like this if you want to use brackets:
1/4(x-12)=12
