Final answer:
Lisa needs to save for 13 full weeks to have enough money to buy a $1,299.99 computer, since she can save $78 per week and already has $347.62.
Step-by-step explanation:
Lisa is saving for a new computer that costs $1,299.99. She already has $347.62 saved. To find out how many weeks she will need to save $78 per week from her job to purchase the computer, we can set up the following equation with the variable w representing the number of weeks:
w = (total cost of the computer - amount already saved) / amount saved per week
w = ($1,299.99 - $347.62) / $78
After calculating:
w = $952.37 / $78 ≈ 12.21
Since Lisa cannot save for a fraction of a week, she would need to save for 13 full weeks to have enough money to buy the computer.