Based on the given diagram, the measure of the arc can be computed using the definition of a circle. One complete revolution of a circle is equal to 360 degrees. If given that we have the arc LJ equal to 240 degrees, the remaining arc, let as x, can be computed as
Solve for the value of x, we get
Finally, to solve for the angle K, we just divide the solved arc measure by half of it, getting
Hence, the measure of angle K is 60 degrees while the measure of the arc that corresponds to angle K is 120 degrees.