The answer is 1/8.
To find this, first set 1/4 to the same denominator as the rest of them, 8.
By doing this, you're new equation is:
x/8 + 2/8 = 3/8
Then, perform a one step equation by subtracting 2/8 from 3/8 which leaves you with your x, 1/8
Hope this helps!