The figure shows two triangles. To find the the area of the shaded region, you have to substract the area of the larger triangle by the area of the smaller:
1. Area of the larger triangle:
A1=bxh/2
b=5 mm
h=2mm+4mm+6mm=12 mm
Then:
A1=5 mmx12mm/2
A1=30 mm²
2. The area of the smaller triangle, is
A2=bxh/2
b=3 mm
h=4 mm
Then, you have:
A2=3 mmx4 mm/2
A2=6 mm²
3. The area of the shaded region is:
A3=A1-A2
A3=30 mm²-6mm²
A3=24 mm²
4. Therefore, the answer is: 24 mm²