You and your friend are selling tickets to a charity event. you sell 12 adult tickets and 6 student tickets for $138. your friend sells 5 adult tickets and 11 student tickets for $100. what is the cost of a student ticket

Let's say the cost of student tickets is x and the cost of adult tickets is y. Then:

(1) 12y + 6x = 138
(2) 5y + 11x = 100

If we rearrange equation (1) we get:
12y = 138 - 6x
Now divide each side by 12:
y = 11.5 - 0.5x

We can now substitute this into equation (2):

5(11.5 - 0.5x) + 11x = 100
57.5 - 2.5x + 11x = 100
8.5x = 42.5
x = 5, therefor the cost of a student ticket is $5.00