65 student tickets were sold
Solution:
Given that movie theater sells student tickets for $ 6 and adults for $ 8
Let "s" be the number of student tickets sold
Let "a" be the number of adult tickets sold
Cost of 1 student ticket = $ 6
Cost of 1 adult ticket = $ 8
Given that theater sold 140 tickets
Number of student tickets sold + number of adult tickets sold = 140
s + a = 140 ------ eqn 1
The theater generated $ 990
number of student tickets sold x Cost of 1 student ticket + number of adult tickets sold x Cost of 1 adult ticket = 990
6s + 8a = 990 ------ eqn 2
Let us solve eqn 1 and eqn 2 to find values of "s" and "a"
From eqn 1,
s = 140 - a ----- eqn 3
Substitute eqn 3 in eqn 2
6(140 - a) + 8a = 990
840 - 6a + 8a = 990
2a = 150
a = 75
Substitute a = 75 in eqn 3
s = 140 - 75
s = 65
Therefore 65 student tickets were sold