help please! can someone also help me understand the formula?

Answer:
solution,
Area of rhombus:
[tex] \frac{1}{2} \times d1 \times d2 \\ = \frac{1}{2} \times (7.5 + 7.5) \times (13 + 13) \\ = \frac{1}{2} \times 15 \times 26 \\ = 195 \: {yd}^{2} [/tex]
Hope this helps...
Good luck on your assignment...