Smith Chart for 300-ohm Load
Note the settings near the top right of this chart. At the top, there are two check boxes that allow you show the admittance and resistance circles. Below that, you can enter the load resistance; R. This allows you to enter the resistance value, but not the reactance value because the goal is to match to a 50 ohm purely resistive device.
Below that are three check boxes that allow you to add circles for the red dot reactance, resistance, and admittance. These will move around as you move the red dot. These suggest the place of the red dot in the larger context of the circles, but does not directly lead to a solution to the problem. The solution comes in output on the left-hand side of the chart.