Two crews were assigned the job of setting a total of 960 conduit hangers. By the time the job was completed, one crew had set only 7/8 as many conduit hangers as the other crew. How many conduit hangers were set by the slower group?

Answer 1

so let the amounts be x and 7/8 x
x + 7/8 x = 960
15/8 x = 960
...

Answer 2

Were did you get 15/8 from?