I'm doing maths homework and I am completely stumped on what to do!! It basically says work out the area from the perimeter! HELP!! Please :(

What shape has been described ?

It depends on the shape that you're working with. For example a circle has area A = \pi D^2/4 and perimeter P = \pi D, so given perimeter length P you can see that D = P/\pi, and hence

A = \pi \frac {(P/\pi)^2} 4 = \frac {P^2}{4 \pi}

For a square you have A = L^2 and P=4L, so given P you have L = P/4 and

A = \frac {P^2} {4^2}