Turns out that I either suck at algebra (likely) or I suck at algebra at 3:20 in the morning (also likely).
In the diagram, Q lies on the joining (0 , 6) and (3 , 0).
OPQR is a rectangle, where P and R lie on the axes and OR = length "t".
(a) Show that QR = 6 - 2t.
I've had a variety of ideas for this, but none of them seem to be quite right. Any help at all would be appreciated.