Final answer:
Michelle would start earning overtime pay after working 4 hours.
Step-by-step explanation:
The equation y = 25x represents Michelle's regular hourly and overtime wage. In this equation, the coefficient of x (which represents the number of hours worked) is 25. This means that for every hour Michelle works, she earns $25.
Since overtime wages are typically higher than regular wages, Michelle would start earning overtime pay when her total earnings exceed her regular earnings. In this case, overtime pay would start when Michelle's total earnings exceed the product of her regular wage per hour and the number of hours worked.
Therefore, Michelle would start earning overtime pay after working 4 hours (when y = 25x = 25 * 4 = 100).