Number of adults: A
Number of students: S
A football game was attended by 550 people ==> Equation 1: A + S = 550
Adults paid $1.20 for tickets; students paid $0.75. Total receipts were $525 ==>
Equation 2: 1.2A + 0.75S =525
Solving for A the first equation:
A + S = 550
A = 550 - S
Using this expression for A into the second equation:
1.2A + 0.75S =525
1.2(550 - S) + 0.75S = 525
Solving for S:
1.2*550 - 1.2S + 0.75S = 525
660 - 0.45S = 525
660 - 525 = 0.45S
135 = 0.45S
S = 135/0.45 = 300
S = 300
Using this value of S into the expression we found for A:
A = 550 - S = 550 - 300 = 225
A = 225
Answer:
225 adults
300 students