Question 478749
We have the area of the garden is 3 * 7 = 21 sq m., if the area of the walk is 11 the total area is 32 sq. m

(7 + x)(3 + x)  = 32 sq. meters.

x^2  + 10x  + 21 = 32

x*2  + 10x  -11 = 0

(x + 11)(x - 1) = 0

x = 1

To check, 4 * 8 = 32 sq m. 
 We can see this does check.
Cleomenius.