It could sometimes be proportional. The reasoning here is that if all the items have different prices it won't be, however if the items you are ordering all have the same price they will be!
Given:

To find:
The simplified fraction.
Solution:
Step 1: Simplify the numerator

Step 2: Simplify the denominator

Step 3: Using step 1 and step 2

Step 4: Using fraction rule:


Cancel the common factor r and t², we get

Cancel the common factors 16 and 3 on both numerator and denominator.



The simplified fraction is
.
The new price is 52.50
30x2=60
30/4=7.5
7.5x3=22.5
22.50+30= 52.50