need someone to help me with my math work

Answer:
The small triangle has a long leg of 8. The triangle area formula is used to derive this. Now, there can be a ration equation.
10/4 = x/8
x = 20
Now use the formula.
A=1/2bh
A=1/2(10*20)
A=100
Area of DEF is 100 m^2.