Answer:
x=6
Explanation:
The triangle is an equilateral triangle since all angles are 60 degrees
That means all sides are equal
3x-13 = x-1
Subtract x from each side
3x-13-x = x-1-x
2x-13 =-1
Add 13 to each side
2x= -1+13
2x = 12
Divide by 2
2x/2 =12/2
x = 6