I am sorry, that is not enough information. You have to show us the graph.
Multiply 4 by its reciprocal: 1/8x1/4= 1/32.
Our objective is to isolate n one side of the equation. The steps are as follows...
a=m-n
(Add n to both sides)
a+n=m-n+n
(The -n and +n cancel out, on the right side of the equation)
a+n=m
(Now subtract a from both sides)
a+n-a=m+a
(The +a and -a cancel out, on the right side of the equation)
n=m+a
Area = (length) x (width)
Area = (10-ft) x (7-ft) = 70 ft²
(Width) / (Area) = (7-ft) / (70 ft²) = 1 / 10-ft .