1)make simultaneous equations with the given data
3.5a (for adults) + 2.5s(students) = 937.5
a + s = 321 (total number of tickets)
2)rearrange the equation
a = 321 - s
3)substitute this equation into the first one and solve the equation
= 3.5(321-s) + 2.5s = 937.5
= 1123.5 - 3.5s + 2.5s = 937.5
= -s = -186
s = 186
-> 186 student tickets
4) with this info, you can easily find the number of adult tickets sold
3.5a + 2.5s = 937.5
3.5a + 2.5(186) = 937.5
3.5a = 937.5 - 465
3.5a = 472.5
a = 135
-> 135 adult tickets
