a = adult tix cost
c = child tix cost
250a + 400c = 22000 and
300a + 800c = 36000 two equations and two unknowns to solve multiply first equation by - 2 to get:
-500a -800c = - 44000 add the two equations
-200a = -8000 solve for a
a = $ 40 use this value in one of the equations to calculate c
300(40) + 800c = 36000
800c = 24000
c = $ 30