How do I solve this problem to find the slope of the line that is perpendicular to
13+-x=y ?

Let's see if I can find a way to get you to think about this without just giving you the answer.

Do you know the formula y = mx + b, where m is slope and b is the y intercept? (If not, it's time to learn it.)

Re-work your equation around until you have it in that format. (You don't really need to "solve" for y. Just keep in mind that if a = b, then b = a. And that a + b is the same as b + a.) Now, what is your m, the slope?

Graph this if you have to and look at how it sits on the graph. And where would the perpendicular line be? By knowing your slope and how it looks on that graph, can you take a guess as to the slope of that perpendicular line? And a hint: don't try to be fancy and make it complicated. :-)

The prependicular slope is just the negative reciprocal of your given slope. Your given slope is -1. What's the negative reciprocal of -1? That's all there is to it.