Write the equations:
a +c = 15
a = 15-c
29.95a + 21.95c = 353.25
Replace a in the last equation:
29.95(15-c) + 21.95c = 353.25
Simplify:
449.25 - 29.95c + 21.95c = 353.25
449.25 - 8.00c = 353.25
Subtract 449.25 from both sides:
-8.00c = -96.00
Divide both sides by -8.00:
c = -96 / -8
c = 12
There were 12 children.