Sandra's bicycle is old and rusty. Her parents won't buy her a new one unless she does more chores around the house. Sandra's dad said he will buy a new bicycle if Sandra mows the lawn, rakes the leaves, and washes the windows every weekend for 16 weeks in a row. Sandra is very motivated and does her chores for 3 weeks straight.
Which equation can Sandra use to find how many more weeks w she needs to do her chores before her parents will buy her a new bicycle?