Take a look at the figures, it's the same angle from a different point of view, so since they are both equal we can set these two equations equal to each other, then solve for 'x':

Distribute 5 into the parenthesis:

Add 10 to both sides:

Subtract 'x' to both sides:

Divide 4 to both sides:

So this is our value of 'x', we can plug it into any of the two equations to find the measurement for both angles:



So the length of both angle E and angle D is 20 degrees.