At the start of the week, you could complete 12 push-ups. By the end of the week, you could complete 17 push-ups. Which proportion could you use to find the percent increase in the number of push-ups

At the start of the week, you could complete 12 push-ups. By the end of the week, you could complete 17 push-ups. Which proportion could you use to find the percent increase in the number of push-ups you can complete? What equation would you use for this?