When y varies directly with x, it means that both x and y are directly proportional.
And then y is directly proportional to x, which menas for ecample, that when x doubles, y doubles too. If x halves, y halves as well.
Also, the ratio of the two measures x and y is always costant
So, [tex] \frac{y}{x} = k[/tex] (k is the costant)
Now, let's find the costant...10/30 = [tex]0. \overline {3}[/tex]
Since we have a recurring decimal, trasform it in a fraction -> 3/9 semplified 1/3
From the formula y/x = k, we find the formula x = y/k
x = [tex]9 : \frac{1}{3}[/tex] = [tex]9 * 3 = 27[/tex]
So x = 27, hope I got it right
