Question 442324
Collect all of your terms into x-terms and y-terms. xs-xt + ys-yt.

x(s-t) + y(s-t). You have x (s-t)s and you have y (s-t)s. You can simplify this one step further into (x+y)(s-t).

So the answer is {{{(x+y)(s-t)}}}