The triangle in the picture is an isoceles triangle meaning that angles P and R are congruent to one another. Here is how to solve the problem:
1. Set the equations equal to one another: 6x-15 = 4x + 5
2. Move the values to have "x" on one side: 2x - 15 = 5....2x=20
3. Divide by 2 to find "x": x=10
X = 10! Hope this helped :)