Answer:

Step-by-step explanation:
we know that
An exterior angle of a triangle is equal to the sum of the opposite interior angles.
see the attached figure to better understand the problem
so
∠DEF=∠ECD+∠CDE
substitute the given values

solve for x
Combine like terms

Group terms



Find the measure of angle CDE

substitute the value of x

Answer:
show everything
Step-by-step explanation:
copy and paste all of all of the problem
Answer:
x/2 + 21 = 36
First we get rid of constants to isolate the variable.
In order to do that we must do the inverse operation.
Inverse operation of addition is subtraction.
-21 -21(subtracting 21 from both sides, whatever we do to the left side we do it to the right side too)
x/2 = 15
inverse property of division is multiplication
x2 x2
X = 30