In ∆OAB, P is the mid-point of AB and Q is the point on OP such that Q = 3/4P. Given that and

The point R on OB is such that OR = kOB, where 0<k<1.

Find, in terms of a, b and k, the vector

I found this:

Given that AQR is a straight line:

Find the ratio in which Q divides AR and the value of k.

I did:

I’m confused to find the ratio & the value of k.

Is it like:

Then…?