Write what the expressions below best represent within the context of the word problem How many quarts of water must be added to 4 quarts of an 80% mixture to obtain a 50% mixture? x represents quarts of water to be added to the % mixture. x + 4 represents the total quarts of the mixture at %.

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?