add 7 to 27 which equals 34
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.
Change first equation
x - 2y = 1
add 2y to both side
x = 2y + 1
Plug into second equation
3(2y+1) - 6y = 3
Distributive property
6y + 3 - 6y = 3
y = 0, plug into first equation
x - 2(0) = 1, x = 1
Solution: x = 1, y = 0
