Answer:
The missing value (x) is 12.
Step-by-step explanation:
Given that there are two values already known, 78° and 78°, we can add them and get 156°.
Since a triangle has a total degree of 180°, we can do this:
180°-156° = 24°
So, now we have the missing angle and its equal to 24°.
what you now do is set 24°= 3x-12 to solve for x.
24°=3x-12
36=3x
/3
12=x
