Solve 80/100 = 68/n using cross multiplication.
80n = 68*100
80n = 6800
n = 6800/80
n = 85
The answer would be n = 85.4/5 = 68/n4/5n = 684n/5 = 684n = 68 * 54n = 340n = 340/4n = 85.