Question 1066973
 The mean of a set of five numbers is 3k.
let n = the number
{{{(5n)/5}}} = 3k
5n = 5(3k)
5n = 15k
 When a sixth number is added to the set, the mean increases by k.
let x = the 6th number
{{{(5n+x)/6}}} = 4k
5n + x = 6(4k)
5n + x = 24k
replace 5n with 15k
15k + x = 24k
x = 24k - 15k
x = 9k
 What is the ratio of the sixth number to the sum of the first five numbers?
{{{x/(5n)}}}
Replace x with 9k; replace 5n with 15k
{{{(9k)/(15k)}}} 
Cancel k
{{{9/15}}} reduces to {{{3/5}}}