Help with this question, please! I don't understand it!

Answer:
18 cm
Step-by-step explanation:
The area (A) of a kite is
A = [tex]\frac{1}{2}[/tex][tex]d_{1}[/tex][tex]d_{2}[/tex], that is
[tex]\frac{1}{2}[/tex] × 8 × [tex]d_{2}[/tex] = 72
4 × [tex]d_{2}[/tex] = 72 ( divide both sides by 4 )
[tex]d_{2}[/tex] = 18 cm