Good afternoon Chelsia! This is just a stacking of vectors like stacking of lego pieces.

Since OA = x + 2y, we draw a vector x from O (which happens to be already provided there as OX), then we draw 2 units of vector Y to end at the point A. Then, we connect O and A together.

We do likewise for B and C.

For PQ, we draw a line from P in the direction OX (movement of +2 units in x and + 2 units in y) and another line from Q in the direction OY (movement of +3 units in x and -1 unit in y). Where they meet, we then count the number of units of x used and the number of units of y used. Take into account the relevant directions in going from P to the intersection point followed by the intersection point to Q.

I will look at this again later if I have time.