Need Help-Cost analysis got me going crazy

So i have two options with a product

Product X

Cost-1.10

Startup-600

Product Y

Cost 1.05

Startup 2500

i want to know how many of product Y i have to buy before the lower cost outweighs the higher startup $$

Here is what i have come up with so far

Cost = 2500+1.05X

Cost = 600+1.10X

Maybe substitution method but i cannot figure out my two initial equations to start with.

i know i can plug in numbers all day to figure out the value, but the fact that i cannot come up with the true math formula will drive me crazy all weekend. Any help would be appreciated :)