In order to subtract mixed fractions, we must convert them into improper fractions first. To do this simply multiply the whole number by the denominator and add the numerator. The product of this operation will be the new numerator (the whole number is no longer present).
(56 + 7)/8 - (12 + 1)/4
= 63/8 - 13/4
Now that we have our fractions in improper form, we must find the least common denominator which is 8. To avoid changing the value of the second fraction, multiply both the numerator and denominator by 2 (which is essentially 2/2 which equals to 1).
63/8 - 26/8
= 37/8