Question

Marta's jump rope is 10" shorter than three times the length of Dilbert's rope. If both their ropes laid together end to end and measured 120" long, how long is Marta's rope?

Answer 1

3d-10+d=120              32.5(3)-10
3d+d-10=120               97.5-10            
4d-10=120                    87.5
   +10  +10
-------------------             Martha's rope is 87.5" long
4d=130
----  ----
  4    4

d=32.5