First we must make each fraction improper. To do so, we must multiply the whole number by the denominator and add the product to the numerator. That would give us 63/8 - 13/4. Now we have to make the denominators the same. To do so, we will just multiply the numerator and denominator of 13/4 times 2 to get 26/8. 63/8 - 26/8 = 37/8. Simplified it is 4 5/8.