It takes Skyler 10 hours to rake the front lawn while his brother, Sergio, can rake the lawn in 6 hours.  How long will it take them to rake the lawn working together?

The answer is 15/4 , or 3.75 or 3 3/4

The question is kind of confusing. if it's asking how many variations of answers can you give. then do 4^5 for your answer.this would be something like the first question could be a and the 2nd c or first b next c etc. if you can, ask the teacher for a better confirmation of what it's asking. if i'm assuming correctly what it's asking, it's 625 different variations.