Question: Chris is way behind on his math homework. He has 100 math problems to complete in total. He completes 12 problems on Monday night. On Tuesday, he completes 3 times as many problems as he did on Monday. On Wednesday, he completes one-quarter of the remaining math problems. How many math problems does he have left to complete on Thursday?
Answer: 
On Tuesday he completes 3 * 12 = 36 math problems.
This leaves him with 100 - 12 - 36 = 52 math problems to complete.
On Wednesday he completes 52 * 0.25 = 13 math problems.
This leaves him with 52 - 13 = 39 math problems to complete on Thursday.