The area of a triangle is calculated using the formula 1/2bh, where b is the base of the triangle and h is the height of the triangle.
Using the diagram, we can see that 8 yd is the base of the triangle and 3 yd is the height of the triangle. The other measurements are most likely just put in there to confuse you.
Substitute 8 for b and 3 for h in the formula.
1/2(8)(3) ==> 1/2(24) = 12
Your answer is B) 12 yd^2.