4/5 is greater than 0.75. That is because, if you turn 4/5 into a decimal, them that decimal will be equal to 80/100. 0.75 is 75/100 as a fraction. 80/100 (4/5 simplified) compared to 75/100 is greater. The answer is yes.
I believe this is the distributive property.
You could convert them into improper fractions first. 7 7/8 should become 63/8 and 3 1/4 should become 13/4. Then, change both fractions so they share a common denominator. I'll use 8.
63/8-26/8 = 37/8, which is then converted into 4 5/8.
Hope that helped you.