See attachment for math work and answer.
Four lbs of granola = 13 lbs
Six lbs of raisins = 12 lbs
13+12=25
25/$2.50=10
5ft 6in = 66 in
2ft 9in = 33 in
66 • 33 = 2178
About 2178 squares inches of plastic will cover the window.
To solve for a variable, you need to get it (x) by itself.
x² - 14 + 31 = 63 Add 31 to -14
x² + 17 = 63 Subtract 17 from both sides of the equation
x² = 46 Square root both sides
x =

Check your work by plugging in

for x and then

.

² - 14 + 31 = 63 Square

46 - 14 + 31 = 63 Subtract 14 from 46
32 + 31 = 63 Add
63 = 63

² - 14 + 31 = 63 Square

46 - 14 + 31 = 63 Subtract 14 from 46
32 + 31 = 63 Add
63 = 63
So,
x is
and 
.