Solve the equation. \dfrac13 + a = \dfrac54
3
1
​
+a=
4
5
​ what is a?

Draw a straight line that continues line DC so that it hits BA. Let the point that hits BA be E.

So you now have the triangle BCE. We can figure out angle BEC to be 85 degrees because a triangle has 180 degrees. Then we can figure out that angle AED has 95 degrees because it forms a supplementary pair with angle BEC.

Then we can figure out angle ADE is 50 because triangle ADE has 180 degrees.

Then finally we can figure out angle ADC to be 130 degrees because it forms a supplementary pair with angle ADE.

Thus angle ADC = x = 130