Answer:
X=12
Step-by-step explanation:
Add the two equations together and equate them to 180 due to the geometrical reason that angles on a straight line add up to 180.
10X-20+6X+8=180 (collect like terms)
10X+6X=180-8+20
16X=192 (Divide both sides by 16)
X=12
Hope that helps :)
