Answer:
x=5
Step-by-step explanation:
We know that a pentagon is in total 540 degrees. From this, we add all other numbers and set them equal to 540 to solve for x.
So, after adding all the angles and setting them equal to 540, we get this.
21x+435=540
21x=105
x= 5
If you want, plug 5 into x and see if it adds up to 540 to check
21(5)+435=540
