Differential equations — practice question

In this chemical reaction, compound $X$ is produced from compounds $Y$ and $Z$. After $t$ seconds from the start of the reaction, the masses in grams of $X$, $Y$ and $Z$ are $x$, $10 - x$ and $20 - x$ respectively. At every instant, the rate at which $X$ is formed is proportional to the product of the masses of $Y$ and $Z$ present at that instant. When $t = 0$, $x = 0$ and $\frac{dx}{dt} = 2$.