So,
Here we have the following vertices:
[tex]\begin{gathered} L(-2,10) \\ K(-1,5) \\ J(-6,5) \end{gathered}[/tex]We are going to write the coordinates of the vertices after a rotation 90° counterclockwise around the origin.
Remember that a 90° rotation counterclockwise around the origin follows the rule:
[tex](x,y)\to(-y,x)[/tex]So what we're going to do is to change the x coordinate of all vertices by each coordinate of y with the opposite sign. And, we're going to change the y-coordinate by the x-coordinate. This is,
[tex]\begin{gathered} J(6,5)\to J^{\prime}(-5,6) \\ K(-1,5)\to K^{\prime}(-5,-1) \\ L(-2,10)\to L^{\prime}(-10,-2) \end{gathered}[/tex]