Which are the specific bits that are puzzling you? I'll start you off:

a) Area of triangle is half base times height.

So let the base be and the height be , and the area be .

Then

But then and .

You can build your quadratic from there by substituting for and 27 for in the equation for the area.

b) The area of a rectangle is height times width. You've been given the variables for height and width, they're x and y. So area = x times y.

As for the perimeter, that's the line that goes round the outside. There's two lengths and two widths. Add those up together and that's the perimeter.

Take it from there.