What is the value of x?

enter your answer in the box.

x =

x=8

Explanation:

The picture tells us that the triangle is equilateral (this means that each angle is 60°). We can assume this because each side has been marked with the same line.

Because each angle is equal to 60°, this means that:

7x+4=60

Now solve for x:

7x=56
x=8

What mathematical statement is missing ? ? the answer is b