I can't solve this. I was able to figure out a problem similar to this but it's different...

Question

At the city museum, child admission is $5.60 and adult admission is $8.80. On Wednesday, 167 tickets were sold for a total sales of $1252.00. How many adult tickets were sold that day?

Answer 1

a+c=167 -> c=167-a

1252=5.6c+8.8a=5.6(167-a)+8.8a=932.2-5.6a+8.8a=932.2+3.2a -> 316.8=3.2a -> 99=a