Translating it into math figures: 4*?-15=9 lets say the question mark is x: 4*x-15=9 4x-15=9 adding 15 from both sides: 4x=24 now divide both sides by 4: x=6 just to make sure it's correct, put it in the original equation 4*6-15=9 24-15=9 :)
The solution to the system is (90,40)....x = adults and y = child's...so x = 90 (there were 90 adult tickers) and y = 40 (there were 40 child tickets)...u already had the answer right in front of you
