Question

Algebra Help Please?

Answer 1

Area of A: 3x

Area of B: 21

Area of C: x^2

Area of D: 7x

Total area of all four rectangles: x^2 + 10x + 21

I'm not sure what's meant by "sum of the area of the large rectangle", but I believe the point of this exercise is to draw the relationship

$(x+3)(x+7)=x^2+3x+7x+21=x^2+10x+21$

which is entirely a consequence of the distributive property of multiplication.