a) W=L-45
b) a=L*W
Use the equation we created in part a and plug it into the area formula.
a=L*(L-45)
9000=L(L-45)
9000=2L-45L
9000=-43L
L= -9000/43
Now to find the width, plug in the length back into the first equation, in part a.
W=(-9000/43)-45
W= -10935/43 (Sorry if you need it in decimal form. Just plug it into a calculator :D)
*Double check my answer to be absolutely sure though