Question

write an equation that relates x and y

Answer 1

there are various answers to that.. any other detail?

Answer 2

if it is directly proportional, say y is directly proportional as x then you'll have, y=kx where k is the proportionality constant

Answer 3

if it is inversely proportional, say y varies inversely as x then you'll have, y=(1/x)k

Answer 4

Your question is not clear.

Answer 5

There are many equation that relates two variables(like x and y).For example linear equation ax+bx=c ; where a,b,c are real number.
Another example, the equation of a straight line y=mx+c where y denotes for value of points of y co-ordinate and x denotes the value of any points of x co-ordinates . and c is constant, any real number.