In this example to calculate the perimeter of a rectangle, the formula used is 2 * (Width + Height)

The variables Width (50) and Height (20) are concatenated together instead of being added. e.g. 5020 rather than 70

This is value is then (correctly) multiplied by 2 to give the perimeter (i.e.. 10040 which is obviously wrong. The answer should be ( 50 + 20 ) * 2 = 140