She will use 12 pounds.
Each pound, one for pepperoni, one for cheese, and one for tomatoes makes 3 per pizza. 4 pizzas, with 3 pounds of ingredients on each makes 12 pounds of ingredients all together.
3/4 - 1/2 = 3/4 - 2/4 = 1/4
7/8 - 2/3 = 21/24 - 16/24 = 5/24
Reasonable because the three items altogether cost about $40
16n+8=4
16n=4-8
16n=-4
n=-4/16
n=-1/4.
