Question

Your class sells 64 tickets to a play. A student ticket cost $1 and an adult ticket cost $2.50. If you collect $109 in total ticket sells, how many adult tickets did you sell?

Answer 1

s + a = 64 ==> s = 64 - a
s + 2.5a = 109

now sub 64 - a in for s in the 2nd equation
64 - a + 2.5a = 109 -- combine like terms
64 + 1.5a = 109 -- subtract 64 from both sides
1.5a = 109 - 64
1.5a = 45
a = 45/1.5
a = 30
Your class sold 30 adult tickets