Answer:
Angle WTS will be 180 degree minus 15x. You can write this as an expression:
180-15x
Now you have an expression for each angle in the triangle. Triangles will always have 180 degrees in them. You can add the expressions together and set it equal to 180. Then you can solve the equation for the x variable.
Explanation:
Angle SWT + angle WTS + angle TSW = 180 degrees
Replace each angle with the expression then solve.