Question 311444
Hey there Gary! I believe I can try to help you. Let's get started.
Well, first off, lets get the prices of the original software. I always find questions out like this in what I consider the most simple way:
(original price)(Percent of price)=(changed price)
So how I would set up one of your problems is 
(x)(1.35)=(285)   the reason why it is 1.35 is because it is 135% of the original price, by the way.
Then, I divide the 1.35 from both sides so the problem looks like this:
x=211.11. 
So the original price of Sammy's software is $211.11. Let's move on.
Now, we'll just do the same thing for Martin.
(x)(1.54)=325  and then divide so:
x=211.04
So Sammy's is just a couple cents more expensive than Martin's!
I guess a way to make this into a linear equation would be to have the y intercept be the original price and the slope would be the percent increase, but I'm not so sure on that part. I'm so sorry! 
I hope this helped you a bit!