Answer: x = -22/7
Step-by-step explanation: Basically, all angles are the same as indicated in the image, this means that the triangle is equilateral and that all sidelengths will be the same lengths
we can now set up an equation that equals both side lengths to find x
4x+16 = -3x -6
4x+16-16= -3x -6 -16
4x = -3x - 22
4x +3x= -3x + 3x -22
7x/7 = -22/7
x = -22/7