So what they are telling you is that 5 is three higher than the variable n.
So n = 5-3
so n is 2.
The formula for finding the area of a square is:

The formula for finding the area of a triangle is:

So for the square the area would be:

The area for the triangle would be:
It would be 7.45 since the -3.05 and the -9.5 together would equal -12.55 which subtracted from 20 would equal 7.45
1.96, if you multiply that by the length, (which is 2.5) then you will get the area of 4.9 hope this helps