Clay collected 7 times as many stamps as Terry. Terry collected half as many stamps as Skylar. Altogether, they collected 140 stamps. How many fewer stamps did Terry collect than Clay?

c = 7t

s = 2t

c + t + s = 140

7t + t + 2t = 140

t = 14

c = 98

c - t = 98 - 14 = 84

84 stamps Terry collected than Clay