At the movie theatre, child admission is $6.30 and adult admission is $9.90 . on monday, 159 tickets were sold for a total sales of $1246.50 . how many adult tickets were sold that day? numberofadulttickets:

C = child tickets
a = adult tickets

Solve this with the substitution method.
Make two equations:

6.30c + 9.90a = 1,246.50
c + a = 159

Solve for c.
Subtract 9.90a from both sides.

6.30c = 1,246.50 - 9.90a
Divide both sides by 6.30.

c = 197.86 - 1.57a (rounded to hundredths)
Plug c into second equation.

197.86 - 1.57a + a = 159
Combine like terms.

197.86 - 0.57a = 159
Subtract 197.86 from both sides.

-0.57a = -38.86
Divide both sides by -0.57.

a = 68.18
round up to ones: 68

were sold.

The correct answer is 10%