To find out how much money Peter saves each week, we can look at the increases in his savings account over the weeks.
- From Week 0 to Week 1: $17.75 - $12.00 = $5.75
- From Week 1 to Week 2: $23.50 - $17.75 = $5.75
- From Week 2 to Week 3: $29.25 - $23.50 = $5.75
Peter saves $5.75 each week.
So, the answer is $5.75.