Given :
The number of tickets sold in the first day : 6 adult tickets and 4 student for a total of $100.
In the second day : 5 adults and 5 students fro $90
Let the price of the adult tickets = x
And the price of the student tickets = y
So, we have the following system of equations :
For the question (2), divide all terms by 5 then solve the equation for x
Substitute with x in the first equation :
So, the price of the student ticket = $4