lets x = # of student tickets
y = = # of non-student tickets
x + y = 2,000 so x = 2,000 - y
10x + 20y = 35,000
substitute x = 2,000 - y into 10x + 20y = 35,000
10x + 20y = 35,000
10(2,000 - y) + 20y = 35,000
20,000 - 10y + 20y = 35,000
10y = 15,000
y = 1,500
x = 2,000 - 1,500
x = 500
answer
# of student tickets = 500
# of non-student tickets = 1,500