First we need to find the least common multiple of the denominators.
40 is is divisible by 8, 5, and 4, so we will use it as our common denominator.
Then we need to multiply the numerators by the same amount we had to multiply each denominator by to get 40.
For example, 8 is the denominator of the first fraction. To make it 40, we multiply by 5. We need to also multiply the numerator 3 by the same 5 to keep the fraction the same. So the 3 becomes 3*5 = 15.
The numerators in order after doing this are 15, -32, -15, and 50. Now add these add.
15-32-15+50 = 18.
Put this sum over the common denominator to get the final answer.
