Rael, Peter and Zane had a total of 839 erasers. The ratio of Peter's erasers to Zane's erasers was 4:3 at first. Rael and Peter each gave away 1/2 of their erasers. Given that the three boys had 502 erasers left, how many erasers did Rael have at first?
r+p+z = 839
p/z = 4/3
r/2 + p/2 + z = 502
solve for r and you get
Rael had 454 erasers at first