There are 100 people in a sport centre. 67 people use the gym.
62 people use the swimming pool.
56 people use the track.
38 people use the gym and the pool.
31 people use the pool and the track.
33 people use the gym and the track.
16 people use all three facilities.
Given that a randomly selected person uses the gym and the track, what is the probability they do not use the swimming pool?

Data from 2005 for various age groups show that for each $100 increase in the median weekly income for whites, the median weekly income of blacks increases by $105. also, for workers of ages 25 to 54 the median weekly income for whites was $676 and for blacks was $527. (a) let w represent the median weekly income for whites and b the median weekly income for blacks, and write the equation of the line that gives b as a linear function of w. b = (b) when the median weekly income for whites is $760, what does the equation in (a) predict for the median weekly income for blacks?