The grasshopper, the frog and the mouse had a jumping contest. The grasshopper jumped 21 inches. The grasshopper jumped 25 inches farther than the frog and the mouse jumped 16 inches lesser than the frog. How much farther did the grasshopper jump than the mouse?
Let's denote the frog's jump by $x$ and the mouse's jump by $y$. Then we have:

$$
\begin{cases}
x + 16 = y \\
x + 25 = 21
\end{cases}
$$

Solving this system of linear equations, we get:

$$
\begin{cases}
x = 5 \\
y = 21
\end{cases}
$$

Now we can calculate the difference between the grasshopper's and the mouse's jumps:

$$
21 - 5 = 16
$$

So, the grasshopper jumped 16 inches farther than the mouse.