So looking at the problem, you are going to want to start by finding a common denominator (1) in this case: yb, and combining like terms (2). You are then going to want to multiply both sides by (yb) as the reciprocal to the fractions (3).
1) 3x 6g
---- = ---
y b
2) 3xb 6gy
------ = -----
yb yb
3) 3xb 6gy
(yb) ------ = -----
yb yb
which becomes: 3xb = 6gy
So after this, things become much more simple, as all you have to do is isolate the (x), which can be done by dividing the entire equation by (3b).
3xb 6gy
----- = -----
3b 3b
where you will then find your answer of:
2gy
x = ----- (simplified by the GCM of 3)
b