Sam had 90 more stickers than Jim. After Sam gave 140 stickers to his brother and 30 stickers to Jim, Sam had 1/2 as many stickers as Jim. How many stickers did Sam have at first?
Sam had 90 more than Jim translates to :
S = J + 90
He gives 140 to his brother and 30 to Jim and now has (1/2) of what Jim has
S - 140 - 30 = (1/2)J
(J + 90) - 140 - 30 = (1/2)J { remember S = J + 90 }
J - 80 = (1/2)J
J - (1/2)J = 80
(1/2)J = 80
J = (2/1) * 80 = 160
S = 160 + 90 = 250 at first