Final answer:
The y-intercept for the function describing Mary's monthly dance club expenses is her fixed monthly fee of $220.
Step-by-step explanation:
The question is asking to identify the y-intercept of a linear function that describes Mary's dance club expenses. The y-intercept is the value of the dependent variable when the independent variable is zero. In this case, the y-intercept is Mary's monthly dance club fee, which is $220. This is because Mary pays $220 every month regardless of how many times she attends the club. This can be seen from the given context where there's a fixed fee (analogous to the $25 or $50 one-time fee in the tutoring and cleaning examples), plus a variable charge per attendance or per session (similar to the tutoring rate of $15 per hour or the cleaning rate of $100 per hour). Thus, the y-intercept is the fixed monthly charge of $220.