Assuming those lines are parallel, then this means the alternate interior angles are the same measure
3x-26 = 2x
3x-26+26 = 2x+26 ... adding 26 to both sides
3x = 2x+26
3x-2x = 2x+26-2x ... subtracting 2x from both sides
3x-2x = 26
x = 26 is the answer