Question

I could use some help to find out Tony’s mistake(s)

Answer 1

To find the shaded area you subtract the area of the triangle from the area of the rectangle:

$A_{shaded}=A_{rec\tan gle}-A_{triangle}$$\begin{gathered} A_{shaded}=w\cdot l-\frac{1}{2}b\cdot h \\ \\ A_{shaded}=(5cm)(11cm)-\frac{1}{2}(5cm)(3cm) \end{gathered}$

Then, Tony's mistake was that he added the areas instead of subtract it.

The shaded are is:

$\begin{gathered} A_{shaded}=55cm^2-\frac{15}{2}cm^2 \\ \\ A_{shaded}=55cm^2-7.5cm^2 \\ \\ A_{shaded}=47.5cm^2 \end{gathered}$

Then, the shaded area is 47.5 square centimeters