Assuming that a month has exactly 4 weeks, the number of days Tonya will visit the athletic club in a month is given by 6 x 4 = 24 visits.
Given that the athletic club charges $15 per month plus $1.75 per visit to club, the amount Tonya will spend in the given month is given by 15 + 1.75(24) = 15 + 42 = 57.
Therefore, for Tonya to be able to meet her goal of working out 6 days per week. she needs to budget $7 more.