Harry has 7 pizzas in total.
Harry gives each friend 4/5 of a pizza.
Simply multiply 7 with the numerator of 4/5:
7 x 4 = 28
Put 28 as the number, and keep the 5 as the denominator so:
28/5
Divide 28 by 5 which equals 5.60.
Harry distributed his 7 pizzas with 5 friends (round down since there can't be 0.60 of a person)