start by finding the measurement missing using the pythagorean theorem
[tex]\begin{gathered} 30^2-12^2=x^2 \\ 756=x^2 \\ x=\sqrt[2]{756} \\ x\cong27.5 \end{gathered}[/tex]add all measurement together to find the perimeter of the backyard
[tex]27.5+30+12=69.5[/tex]if the bushes are wanted 3 feet appart from each other divide the perimeter by 3
[tex]\frac{69.5}{3}\cong23[/tex]Mrs. Cheung's backyard is going to need 23 bushes
