[philosophy 422] this is sentential logic:
how many distinct ways are there of restoring brackets to form wffs (well-formed formulas) out of the following string?
~p & q -> ~r v s
, also explain why so i can understand. you!

What is the missing step in this proof ?

Aretha wanted to gather data about the cost of local bowling leagues in her area. she plotted the data and determined that the average bowling league costs consist of a one-time registration fee and a monthly fee modeled by the equation y = 15x + 20. identify and interpret the y-intercept in this model. the y-intercept is 20. this is the cost per month. the y-intercept is 20. this is the cost of registration. the y-intercept is 15. this is the cost of registration. the y-intercept is 15. this is the cost per month.

Math it's appreciated. (picture provided)