quadratic word problems

[leekiss]

A rectangle has an area of 60 square millimetres. If the length and width were each increased by 5 millimetres, the area would be 180 square millimetres. Find the dimensions of the original rectangle.

Could someone please help me! I have tried everything.

The answers are 4mm and 15mm.

[Muzza]

Let the length be x mm, and the width be y mm. What can you say about x and y? What can you say about x+5 and y+5?

[recon]

(x + 5) x (y + 5) = 180

Expanding,
xy + 5x + 5y + 25 = 180

The value of xy is given in the question. Plug in into the equation above. The rest should be easy.