Answer:
x=13
Explanation:
the angles shown are vertical angles so they are going to have the same value so to find x we setup an equation and the equation would be
 -3x+14=-x-12 and the we solve for x
step 1 add 3x to each side 
14=2x-12
step 2 add 12 to each side 
26=2x 
step 3 divide each side by 2
x=13