The 2 is the name of the angle ? Or its degree? I assume it's the name of the traiangle because there is no degree symbol on the 2
6x+12=60
6x=48
x=8
An equilateral triangle is a triangle with all three sides of equal length. An equilateral triangle also has three equal 60 degrees angles. That's why I equalled 6x+12 to 60.