There are 500 computers in an office building. the it manager randomly chose 40 computers to be inspected for viruses. of those inspected, 6 computers had viruses. what is the best estimate of the percent of computers in the building that have viruses?

Which one ? is the answer and how to find this answer

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?

What is the distance between the points (2, 5) and (5,9)?