$\sec(\theta)=x/5$.
What does $\sin(\theta)$ equal? What does $\tan(\theta)$ equal?
$\sec(\theta)=x/5$.
What does $\sin(\theta)$ equal? What does $\tan(\theta)$ equal?
As Michael Chen has alluded to:
Start by noting that
$\sec \theta = \frac{1}{\cos \theta} = \frac{x}{5}$
so that $\cos \theta = \frac{5}{x}$
Now you know that $\cos \theta$ is the 'adjacent / hypotenuse ' of a right angled triangle. So...draw the triangle, and work out what the unknown side ('opposite') will be, and then use the definition of $\tan$ and $\sin$.