The school that Norachai goes to is selling tickets to the annual dance competition

Question

The school that Norachai goes to is selling tickets to the annual dance competition. On the first day of ticket sales the school sold 6 senior citizen tickets and 11 child tickets for a total of $172. The school took in $230 on the second day by selling 9 senior citizen tickets and 13 child tickets. What is the price each of one senior citizen ticket and one child ticket?

Answer 1

6S + 11C = 172

9S + 13C = 230

multiply 1st by 3 and 2nd by 2 then subtract to eliminate S

18S + 33C = 516

18S + 26C =460

7C =56

C = $8

6S = 172-88 = 84

S = 84/6 = 42/3 = $14