First, write the problem out with vertical fractions. In the first fraction, you have 1 on the top and 4a on the bottom. In your second fraction, you have 2 on the top and 3 on the bottom. Put an = sign between them, and you've written out your problem. This will help you visualize what I'm going to tell you next. In the numerators of your equation, you can work backwards and see that to get from 2 to 1, you have to divide by 2. This means that to get from 3 to 4a, you have to divide by 2 as well. 3 divided by 2 is 1.5, or 3/2. But since what you solved for was 4a, you need to divide by 4 to isolate a. 3/2 divided by 4 is equal to 3/8. Your answer: 3 over 8.