Question

x varies directly with 5y and x=15 when y=75.find the value of y when x =7

Answer 1

just see.. x veries in with 5y...and here x is given as 15..in first part of the question so...
here ×=5×15
= 75..
in same way...
when x=7...then
...x=5y
=5×7
=35

Answer 2

x varies as 5y
or x = 5ky (k= proportionality constant)
Now x =15 and y= 75
Therefore 15 = 5*75 k
or k =1/25
Now x=7 then
7 =5y/25
or y = 35