Give the step-by-step reasoning process and then the final answer. Ben starts each day with $50, spends $15 every day and saves the rest. After a few days, his mom doubled his total savings and his dad gave him an additional $10. If he now has $500, How many days have elapsed?
Let the number of days be x. He saves $50 - $15 = $35 each day. After x days he had saved $35 * x = $35x. His mom doubled his savings to give $35x * 2 = $70x. His dad added $10 to give $70x + $10 = $500. Subtracting 10 from both sides of the equation formed gives $70x = 490. Dividing both sides by $70 give x = 7 days.
The final answer: 7.