A box of cupcakes cost $6 while a box of croissants cost $7. Each box contained either 10 cupcakes or 4 croissants. Xylia bought the same number of cupcakes and croissants. She paid $115 more for the croissants. How many boxes of cupcakes did she buy?
To make the number of cupcakes and croissants that Xylia bought the same, find the LCM of 10 and 4.

LCM of 10 and 4 = 20

Cost of 1 set of 20 cupcakes
= 6 x 2
= $12

Cost of 1 set of 20 croissants
= 7 x 5
= $35

Amount that Xylia paid more for 1 set of 20 cupcakes than 1 set of 20 croissants
= 35 - 12
= $23

Number of sets of $23
= 115 ÷ 23
= 5

1 set of $23 → 4 boxes of cupcakes

5 sets of $23 → 5 x 4 = 20 boxes of cupcakes

Number of boxes of cupcakes that Xylia bought = 20

Answer(s): 20