I got yah! Do you want a direct answer or show work?
Direct answer x= -3 y=4
A square has the same width and height, so find the gcd of 90 and 126. Here are there factors:
90:1,2,3,5,9,10,15,18,30,45,90
126:2,3,6, 7,9,14,18,21,42,63,126
18 is the largest in both so the number of squares will be
90/18 * 126/18
= 5*7 = 35
3+7=10 because three and seven are both in your equation so after adding 3 and 7 all you must do is add 5 to 10
The function is f(x)=2x+10