X = 9
All of the equations are equal since it is an equilateral triangle.
So, just pick two equations and solve them.
3x - 1 = 2(x + 4)
distribute
3x - 1 = 2x + 8
add 1 to both sides
3x = 2x + 9
subtract 2x from both sides
x = 9
DOUBLE-CHECK (If you want to)
4x ÷ 2 + 8 = 3x - 1
subtract 8 from both sides
4x ÷ 2 = 3x - 9
simplify
2x = 3x - 9
subtract 3x from both sides
-x = -9
divide both sides by -1
x = 9
TRIPLE-CHECK (If you want to)
4x ÷ 2 + 8 = 2(x + 4)
simplify
2x + 8 = 2x + 8 (It's already equal)