Each child ticket for a ride costs $3, while each adult ticket costs $5. the ride collected a total of $150, and 40 tickets were sold. how many of each type of ticket were sold?
a. 150 child and 40 adult
b. 24 adult and 10 child
c. 30 child and 10 adult
d. 25 child and 15 adult

The way to go about this is to think logically about the answers
A) isn't possible as 40 tickets were sold and 150 plus 40 = 190
B) is similar to above only there was less than 40 tickets sold
C) very possible
D) very possible
next step:
C) (30 x 3) + (10 x 5) = 90 + 50 = $140 (by this we should assume that the answer is D) 
D) (25 x 3) + (15 x 5) = 75 + 75 =  $150 ( yay answer is D :) )

24 students walk to school