Vectors and co-linearity

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If two vectors a and b are non-collinear, then for what values of x are the vectors $$c = (x-2)a + b$$ and $$d = (3 + 2x)a - 2b$$ collinear?

No idea how to even approach the problem. I attempted drawing a diagram, but it didn't seem to help. Please point in the right direction!

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I'll give you a hint, if c and d are co-linear for certain value of x then that means the angle between them is zero. Hence cross product c x d = 0

Now all you gotta do is solve the equation:

(3+2x) + 2(x-2) = 0