The probability of Jack hitting a target is 1/4. How many times must he fire so that the probability of hitting the target at least once is greater than 2/3?

using the formula $(nCx)({p}^{x})(({p}^{\prime}{)}^{n-x})$

I identified $p=1/4$, ${p}^{\prime}=3/4$, $x=?$, $n=?$

in order to solve this que, I have to solve x but i couldn't identified it.

using the formula $(nCx)({p}^{x})(({p}^{\prime}{)}^{n-x})$

I identified $p=1/4$, ${p}^{\prime}=3/4$, $x=?$, $n=?$

in order to solve this que, I have to solve x but i couldn't identified it.