What's the area of the shaded region?

To find for the left side of the missing length of the triangle, I subtracted 3 cm from 7 cm  to get 4 cm. (7−3=4 cm)
To find for the bottom side of the missing length of the triangle, I subtracted 3 cm from 6 cm to get 3 cm. (6−3=3 cm)
Now, I will find the area of the unshaded region.
A =  × base × height
A =  × 4 × 3
A = 6 cm²
Then I will solve for the shaded region.
A = base × height
A = 7 × 6
A = 42 cm²
Subtract the area of the unshaded region from the area of the shaded region. (42 cm² − 6 cm² = 36 cm²)
The answer is 36 cm².