Final answer:
The problems presented involve high school level mathematics, covering topics such as determining probabilities using z-scores and the normalcdf function, and making predictions based on linear equations.
Step-by-step explanation:
The question posed involves finding the difference in cost between two job efforts, calculating z-scores for probabilities, and predicting scores using a linear equation. In each case, you're manipulating or interpreting algebraic equations and statistical measures, indicating that the subject matter falls within the realm of High School Mathematics.
For example, when finding the probability that a household personal computer is used for entertainment between 1.8 and 2.75 hours per day, you first calculate the z-scores and then use the normalcdf function to find the probability, which comes out to 0.5886.
To predict the math test score for a student who practices a musical instrument for five hours a week, you would use the given linear equation ë = 72.5 + 2.8x and substitute 5 for x to make the prediction. Similarly, when comparing the costs between two jobs, the algebra involves finding the difference in hours required and multiplying by the cost per hour to determine the additional cost.