A good place to start is gathering the x terms on one side.
So for a this would be
x - 3x/2 + 4 = 0
Then we collect like terms
-x/2 + 4 = 0
You might already see that x=8 is the solution
If you don't see that yet, add x/2 to each side, then multiply each side by two.
b looks a bit trickier, but it isn't as bad as it seems.
We can multiply the whole equation by 3 to get rid of most of the fractions if you'd rather not work with them.
Once you've expanded out the brackets, you can then collect like terms (like we did for part a). From there, it should be fairly simple to find the solution.
I'm leaving that here since I'm on mobile, but hopefully this helps you get a start
If you're still having trouble, reply back with what you've tried and you'll be helped through