Answer:
x = 7
Explanation:
Because the points are collinear:
AB + BC = AC
We'll plug in the expressions in terms of x.
(-1 + 2x) + (11) = (3x + 3)
And solve for x. Combine like terms on the left
2x + 10 = 3x + 3
Subtract 3 on both sides
2x + 7 = 3x
Subtract 2x on both sides
7 = x