I think you want to know about the value of x and y. Based on this assumption, i am answering the question.
y = x + 5
20x + 25y = 1115
Putting the value of y from the first equation in the second equation, we get
20x + 25(x + 5) = 1115
20x + 25x + 125 = 1115
45x = 1115 - 125
45x = 990
x = 22
Then
y = x + 5
= 22 + 5
= 27
From the above deduction, it can be concluded that the elementary classroom will have 22 new desks and the secondary classroom would have 27 desks.