To find percentage decrease, we need to see how "much" of 120 was taken off.
So, let's call the percentage x (the percentage in decimal form).
120 * x = 78
so,
78/120 = x
.65 = x
So, our percentage in decimal form is .65, to get it to an actual percentage, we multiply it by 100 (since a percentage is out of 100)
The percentage decrease is 65%
