Let a and b be the sides of the rectangle.

We can calculate the area of the shaded area as follows:

( a x b) / 2 + (a x b) /4 = 42

Let the first term of the equation be equal to X, and the second term be equal to X/2

We can write the above equation, as follows:

X + X/2 = 42 Solving the equation, it gives X = 28

Then the area of the rectangle is 28 x 2 = 56