Question

After the math contest, Basil noticed that there were four extra-large pizzas that were left untouched. In addition, another three slices of pizza were uneaten. If there were a total of 51 slices of pizza left, how many slices does an extra-large pizza have

Answer 1

s = number of slices for a large pizza

so if "s" is the number of slices in 1 large pizza, the total for 1 pizza will just be 1s, for two pizzas will be 2s and so on, so for 4 pizzas the total will just be 4s.

we also know there were an extra 3 slices, and we also know that whatever 4s is plus 3 will give us the total of 51 slices of pizza.

$4s + 3 = 51\implies 4s = 48\implies s = \cfrac{48}{4}\implies \boxed{s = 12}$