Length of the rectangle = (8x + 5) cm
Breadth of the rectangle = (5x + 3) cm
Area of rectangle = length × breadth
= (8x + 5)(5x + 3)
= 8x(5x + 3) + 5(5x + 3)
= 8x × 5x + 8x × 3 + 5 × 5x + 5 × 3
= 40x2 + 24x + 25x + 15
= 40x2 + 49x + 15
So, area of rectangle is (40x2 + 49x + 15) cm2.