Answer:
You sold 20 student tickets.
Step-by-step explanation:
Given that:
Total tickets sold = 27 
Total amount collected = $170
Cost of student ticket = $5
Cost of adult ticket = $10 
Let,
x be the number of students tickets sold 
y be the number of adult tickets sold 
x+y = 27          Eqn 1
5x+10y=170     Eqn 2
Multiplying Eqn 1 by 10
10(x+y=27)
10x+10y=270     Eqn 3
Subtracting Eqn 2 from Eqn 3
(10x+10y)-(5x+10y)=270-170
10x+10y-5x-10y=100
5x=100
Dividing both sides by 5 

Hence,
You sold 20 student tickets.