Question

The fencing along the rectangle's width costs £8 per meter. Also, the fencing along the rectangle's length costs £10 per meter. If the perimeter is 280 meters, express the cost C as a function of width w.

So far I've done:
C = 2w(8) + 2l(10)
C = 16w + 20l
280 = 16w + 20l
l = (280-16w)/(20)
C(w) = 16w + 20 ((280-16w)/(20)) = 280
But when I try to submit 280 it tells me it is incorrect. What am I doing wrong?
Thank you!

Answer 1

So far I've done:

C = 2w(8) + 2l(10)
C = 16w + 20l
280 = 16w + 20l **************** no**** 280 = 2 w + 2 l