multiply through by 2a, you will get2/a = 1/2 + 3/a
4 = a + 6
can you continue?
or perhaps an easier way for you to follow is to get all a's on one side. so you would begin by subtracting 3/a from both sides to get:
2/a - 3/a = 1/2
adding the fractions on the left becomes
-1/a = 1/2