Q. To what product in standard form is $\displaystyle C_{20}$ x $\displaystyle C_{30}$ isomorphic?

I got... $\displaystyle 20 = 2^2 \cdot 5 = 4 \cdot 5$ and $\displaystyle 30 = 2 \cdot 3 \cdot 5$

But how do i arrange these? I imagine it should be something like $\displaystyle C_{2 \cdot ---}$ x $\displaystyle C_{3 \cdot ---}$ But im not sure where the 5's and the 4 should go.

On a side note how do i put letters into latex so that they look like x and not $\displaystyle x$?