We know that since a diameter splits a circle in half, the arcs EF, FG, and GH must add up to 180°, half the measure of a full circle. We can then use the arc addition property to create an equation using the information we know. This equation would be (10x + 8) + 67 + 11x = 180. This can be simplified to x = 5. Therefore, the value of x is 5. Now, we can simply plug in the value of x into the expressions for EF and GH. This means that the measure of EF is 58° and the measure of GH is 55°.
