A picture of dimensions 20cm*15cm is to be framed with a 2cm wide frame . find the area of the frame

Assuming the height of the picture is 20cm. The frame is 2cm wide. Then you have to add 2cm above plus 2cm below, giving you total height of 24cm.

Same goes for the width: 15cm + 2cm on either side gives you 19cm.

The whole thing has then an area of

24cm * 19cm = 456cm²

The area of the frame equals the difference of the total area and the area of the picture:

Area of the picture:
20cm * 15cm = 300cm²

Difference of the two:

Frame area:
456cm² - 300cm² = 156cm²

Cost of framing at the rate of $15 per sq.cm:
156 * 15 = $ 2340

That's way too expensive.