I'll make up a problem similar to yours which can be solved:
A ticket for an adult costs $40 . A ticket for a child costs $28. The total
collection from the sale is $23004. If the price of a child's ticket had cost
only $24, the total collection would have been $20952. how many adult and
children tickets were sold.
Let A = the number of adult tickets were sold
Let C = the number of adult tickets were sold
40A + 28C = 23004
40A + 24C = 20952
Subtracting the two equations gives
4C = 2052
C = 513
Substituting in the second equation
40A + 24(513) = 20952
40A + 12312 = 20952
40A = 8640
A = 216
216 adult tickets were sold. 513 child tickets were sold.
Edwin