6 books at $ 8 = (6 * 8) = 48
if he got a discount of 20%, then he paid 80%
0.80(48) = 38.40 <== what he paid
Consider the number as 'n' (for now)
3n - 9 = 69
3n = 69 + 9
3n = 78
n = 78/3
n = 26
Therefore, The number is 26
You would do percent of change.
meaning you would subract 65 and 50 to get 15. then you would put 15 over 50 (as a fraction) then equals r/100. then you would cross multiply to get r.
orginal:50
new:65
65-50=15
15/50=r/100
15r=5000
then divide by 15 to get r
