QUADRATIC EQUATIONS HELP HELP

Arthur wants to fence three sides of his rectangular garden. The fourth side of the garden faces into the back of his house. He has 80 metres of fencing. Let x represent the width of his garden and let y represent the length of his garden. i) show that y = 80-2x ii) write an expression for the area of the garden in terms of x iii) if the garden has an area of 487.5m^2 find two possible values for the width and length of the garden How would I answer these I'm so stuck

roro123— 27/10/16