Area of a rectangle can be calculated by multiplying the length by the height.
So:
l x w
3 x 13
39 cm squared
Area of a triangle can be calculated by multiply the length by the height and dividing by two. So:
1/2 x l x w
1/2 x 10 x 8
40 m squared

The number "x" is given by:
Therefore, we have:
Multiple the 2 numbers and you should get 0.594
Explanation is the pic