<span>Let the number be x.
The quotient of negative 1 and the product of a number and 21 is -1/21x</span>
The answer is 102 because you subtract 180-78.
The first step is to calculate the total number of pizza slices there are.
We know each slice is 1/8 of the pizza. (think of 1/8 as 1 out of 8 pieces)
This means each pizza has 8 slices.
There are 3 pizzas so there are 8 x 3 = 24 slices total
Next we want to figure how many slices of pizza they ate which will help us figure out how many are left.
They ate 3/4 of the pizza, so in other words only 1/4 of the pizza is left.
In order to figure out how many slices are left, all we need to do is find out what 1/4 of the total number of slices are.
# of slices left = Total number of slices x 1/4 (1/4 of the pizza is left)
# of slices left = 24 x 1/4 = 24÷4 = 6
This means there are 6 slices of pizza left.
