The two labeled angles are alternate interior angles, and as such, they are the same.
From this result you can build the equation
[tex] 15x-2 = 13x+2 [/tex]
and solve it for x: subtract 13x from both sides to get
[tex] 2x-2=2 [/tex]
and add 2 to both sides to get
[tex] 2x = 4 \implies x = 2 [/tex]
Check: if we plug the value we found we have
[tex] 13\cdot 2 + 2 = 26+2 = 28 = 15\cdot 2 - 2 = 30-2 [/tex]
So the angles are actually the same, as requested.
