Answer:
135 minutes
Step-by-step explanation:
36 cupcakes in 45 minutes can be written as

, so to find how long 108 will take, you can find it by equating these two fractions:

=
Simplify by cross division:
divide 45 and 108 by 3 to simplify into this:

=

x = 15
The rate is 3, so 45 • 3 = 135 minutes.
Another way of looking at it is this:
108 ÷ 36 = 3 this is the rate that you need to multiply the amount of time that it takes to make the cupcakes, so:
45 • 3 = 135 minutes.