Help need because i´m stuck

  594 in²

Step-by-step explanation:

There are several ways to do this.

Given the way the figure is dimensioned, the last strategy is the easiest.

A rectangle that surrounds the entire figure will be 36 inches wide and 22 inches high. The white space rectangle in the lower right corner is shown to be 18 inches wide and 11 inches high.

The area of a rectangle is the product of its length and width:

  A = LW

So the difference in area between the "bounding" rectangle and the whitespace rectangle is ...

  shaded area = (36 in)(22 in) -(18 in)(11 in) = 792 in² -198 in²

  shaded area = 594 in²

Additional comment

You can also recognize that the dimensions of the cut out corner are each half the overall dimensions. That means the shaded area is 3/4 of the overall "bounding" rectangle. There are several ways you can make use of that fact.