Answer: 47.5 cm^2
Step-by-step explanation:
Tony's mistake is that he added the area of the rectangle and triangle. Instead you should subtract the area of the triangle from the rectangle.
1. The area of the rectangle is 5*11 = 55 cm^2
2. The area of the nonshaded triangle is 5*3*(1/2) = 7.5 cm^2
3. The area of the shaded region is the area of the rectangle minus the area of the triangle. This equals 55 - 7.5 cm^2 = 47.5 cm^2
