It takes Sisyphus two days to carry a pile of rocks up a hill. When I helped out, it took us only 1.2 days to carry all of the rocks. How long would it take me to carry the rocks by myself?

Answer 1

rates add:
books/1.2=books/my time + books/2days

multiply both sides by
my time*1.2*2/books

2*mytime=1.2*2+mytime*1.2

mytime(2-1.2)=2.4
my time=3days

Answer 2

1/2 + 1/x=1/1.2
1.2x+2.4=2x
.8x=2.4
x=3 days working by yourself. ☺☺☺☺