A street vendor sells two type of newspapers, one for $0.25 and the other for $0.40. If he sold 100 newspapers for $28.00, how many did he sell at $0.25?
+128474 Let N be the number of newspapers sold at 25 cents
Then 100 - N is the number sold at 40 cents
Then
number sold at 25 cents * price each + number sold at 40 cents * price each = 28
N * .25 + (100 - N) * .40 = 28 simplify
.25N + 40 - . 40N = 28
-.15N + 40 = 28 subtract 40 from both sides
-.15 N = -12 divide both sides by -.15
N = 80 at 25 cents
