we have a circle first we will calculate the whole area of the circle using the next formula
[tex]A=\pi r^2[/tex]where r= 13 units
[tex]A=\pi(13)^2=530.93\text{ square units}[/tex]Then we have 54° we need to divide between 360 In order to know the part of the circle we have
[tex]\frac{360}{54}=\frac{20}{3}[/tex]so in order to know the area of the sector HJK we will divide the area between 20/3
[tex]A_S=\frac{A}{\frac{20}{3}}=\frac{530.93}{\frac{20}{3}}=79.63[/tex]