Hook's law states that
[tex]F=k\Delta x[/tex]
where F is the applied force, k is the spring constant, and [tex]\Delta x[/tex] is the change in length.
Plugging your values, we have
[tex]7.5 = 0.289\Delta x \implies \Delta x = \dfrac{7.5}{0.289}\approx 25.95[/tex]
