approximately how many times greater is 5×10^8 than 8×10^5 ?

God's gym charges a sign-up fee of $100 plus $30 per month. write an expression to represent how much someone would pay for a membership.

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?

I’m still confused on how to work the percentages