system of linear equations (elimination)

Question

1. Rico bought 3 adult tickets and 5 child tickets for a total of $50.
2. Sasha bought 1 adult ticket and 5 child tickets for a total of $31.

The system of linear equations shown represents this situation, where x is the cost of an adult ticket and y is the cost of a child ticket.

{3x+5y=50x+5y=31

How much will Julia pay for 7 adult tickets and 5 child tickets? 

Julia will pay $

.00

Answer 1

3A + 5C = 50

1A +5C = 31

7A + 5C = ?

subtracting the 2nd equation from the 1st gives 2A = 29, or A=29/2 = $14.50 for an adult ticket

C= 31/5 - 14.5/5 = 6.20-2.90 = $3.30 for a child ticket

7(14.5)+ 5(3.3) = 101.5 + 16.5 = $118.00 for 7 adult & 5 child tickets