Step-by-step explanation:

If it helps, write as a product of fractions, grouped by variable.

Now reduce using exponent rules.

Solution:
Area of parallelogram
= b × h
= 20 × 16
= 320 in^2
Area of triangle
= 1/2 × 20 × 8
= 80 in^2
Area of figure
= 320 + 80
= 400 in^2
Yes...the person's hypothesis could be correct.