Question 1057120

b = number rotten = 24   (given)
r = number ripe
u = number unripe

r = u + 18   ("18 more ripe than unripe")
r + u = 84-24   ("84 oranges, 24 were rotten, the rest were either ripe or unripe")

Substitute the right hand side of the top equation into the bottom:
(u + 18) + u = 84-24
2u + 18 = 60
2u = 42
u = 21   —>  r = 39

ripe/rotten = 39/24 = 1.000/0.615 = 1.626/1
ripe/unripe = 39/21 = 1.000/0.538 = 1.859/1