Question

Anyone know the answer for this

Answer 1

Both of these angles are co-interior angles, and co-interior angles always add up to 180.

You can use this information to make an equation:
3x + 6 + 123 = 180

Then you just need to simplify to make x the subject:
3x + 129 = 180
3x = 51
x = 17

Answer: x = 17