Peter is thrice as old as his sister. Six years from now, he will be 2 years more than twice his brother's age. How old are they?

Two things:

1. We don't provide homework answers, but we will help you along. Show us your attempt at setting up the equation(s) for this problem, and we'll help if you get stuck.

2. In the problem statement you mention a sister in the first sentence and a brother in the second. This problem involves Peter and one sibling, not two.

I set up a formula to start figuring it out. Did you? Start with Peter and the sister. Once you get that another formula can be written and solved rather easily.

What did you get for the first part of your question?