Answer:
Step-by-step explanation:
a = adult cost
c = child cost
a = c + $3
200a + 100c =$2100
^ each # of tickets sold
200(c+3) + 100c =$2100
200c + 600 + 100 c = 2100 combine like terms
300c + 600 = 2100 need variable only on one side of equal sign so you subtract 600 from each side of the = sign
300c = 1500 now divide by 300 on both sides to isolate variable
c = $5
