Reciprocals and boat speeds

You will solve a pair in $\dfrac{1}{x}$ and $\dfrac{1}{y}$ by changing letters, and turn the times of a boat into its speed and the speed of the stream. The function solve_pair is written for you.

Your tasks.

1. In solve_recip, solve $\dfrac{a_1}{x} + \dfrac{b_1}{y} = c_1$ and $\dfrac{a_2}{x} + \dfrac{b_2}{y} = c_2$. Let $u = \dfrac{1}{x}$ and $v = \dfrac{1}{y}$, solve for $u$ and $v$ with solve_pair, and return (1 / u, 1 / v).
2. In boat_speeds, return (boat, stream) in km/h. The speed downstream is the distance divided by hours_down, the speed upstream is the distance divided by hours_up, and the two speeds give the boat and the stream.
3. Set ans to the speed of the boat when $30$ km downstream takes $2$ hours and $30$ km upstream takes $3$ hours.