There are two kinds of tickets general and student
Total sale is 4500
the equation is 4500 = 15X + 9Y
where X is general and Y is student
if 150 general were sold that means
4500 = 15•150 + 9Y
so then Y = (4500- 2250)/9 = 2250/9 = 250
Remarks
writing in standard form
4500 - 15X - 9Y = 0
Another name for standard form is a scientific notation, that means express the numbers in powers of 10.