She bought 54 child tickets and 19 adult tickets.
Step-by-step explanation:
No. of tickets purchased = 73
Cost of tickets = $771
Cost of one child ticket = $9
Cost of one adult ticket = $15
Let,
Child ticket = x
Adult ticket = y
According to given statement;
x+y=73 Eqn 1
9x+15y=771 Eqn 2
Multiplying Eqn 1 by 9;
[tex]9(x+y=73)\\9x+9y=657\ \ \ Eqn\ 3\\[/tex]
Subtracting Eqn 3 from Eqn 2;
[tex](9x+15y)-(9x+9y)=771-657\\9x+15y-9x-9y=114\\6y=114\\[/tex]
Dividing both sides by 6;
[tex]\frac{6y}{6}=\frac{114}{6}\\y=19[/tex]
Putting y=19 in Eqn 1
[tex]x+19=73\\x=73-19\\x=54\\[/tex]
She bought 54 child tickets and 19 adult tickets.
Keywords: linear equations, subtraction
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