Final answer:
Both Jose and Mary made mistakes in their simplification. The correct simplification of the expression 3y + y - 8 - 9 is 4y - 17, not 3y - 16 or 4y - 16.
Step-by-step explanation:
The problem in question involves simplifying an algebraic expression: 3y + y - 8 - 9. To solve this, combine like terms. Firstly, the 'y' terms: 3y and y add up to 4y, not 3y. Next, combine the constants: -8 and -9 become -17. Therefore, the correct simplified expression is 4y - 17, not 3y - 16 nor 4y - 16.
Mary made the mistake by combining the constants incorrectly as -8 and -9 add up to -17, not -16. Jose's mistake was also in not adding the 'y' terms correctly. Thus, the correct answer is actually slightly different from both of their answers.