Rectangle Problem

In this question you are asked to find the area of triangle BEF

So firstly we need to find the dimensions of the rectangle.

P= 2(18)+ 2x

56=36+2x

2x= 20

x=10

Now we know the dimensions

So if we know the area of triangle of ABE and subtract the area of ABF from it, we can find the answer.

That is:

BEF = ABE- ABF

So,

 Area of ABE=  1/2 (18 x 10)

= 90

BEF = ABE- ABF

= 90-42

=48

Hence, the area of triangle BEF is 48.