Hello, thank you for taking the time to post your question!
You just want to equate the two expressions and then solve for the value of t … on this one that means taking
18000 + 2500t = 8500t
18000 = 6000t
t = 3
meaning that it will take 3 months for the total expenses to match the total profit
I hope that helps you get moving in a better direction on this type of question! Feel free to reach out if you have any additional questions beyond that :)