A gym instructor has a total of 60 hand weight in her studio. Some of the hand weights are 3 pound weights and the rest are 5 pound weights. If there are 10 more 5-lb weights than 3-lb weights, then how many of each kind does she have?
Let x = number of 3-lb weights
Then x + 10 = number of 5-lb weights
Since there are a total of 60: x + (x + 10) = 60
x + x + 10 = 60
2x + 10 = 60
2x = 50
x = 25 (number of 3-lb weights)
x + 10 = 35 (number of 5-lb weights)