3. If Mary starts with \( \$ 10 \) in her savings account and wants to add \( \$ 20 \) each week to save for a new phone that costs \( \$ 150 \), how many weeks will she need to save before she has enough money? Write an equation that represents how Mary will save her money.

To find out how many weeks Mary needs to save, we can model her savings with the equation: \( S = 10 + 20w \), where \( S \) is the total savings and \( w \) is the number of weeks. She needs to save at least \( \$ 150 \), so we set up the inequality: \( 10 + 20w \geq 150 \). Solving for \( w \): 1. Subtract \( 10 \) from both sides: \( 20w \geq 140 \) 2. Divide both sides by \( 20 \): \( w \geq 7 \) Therefore, Mary will need at least **7 weeks** to save enough for her new phone! Mary's journey doesn't just give her a new phone; it also reinforces the value of setting financial goals! Every week she adds her savings, she sees progress, turning her small initial amount into a meaningful goal. Not only does she get the phone, but she also learns a great lesson in patience and planning.