Task 1. A butcher at the market sold a calf, a calf, and a sheep. The calf and the sheep together weighed $90 \mathrm{~kg}$, the calf and the calf $186 \mathrm{~kg}$, and the sheep and the calf 240 $\mathrm{kg}$. How many kilograms does each animal weigh?
Solution. From the given data of the problem, we have

$$
\begin{aligned}
& J+O=90 \\
& J+T=186 \\
& O+T=240
\end{aligned}
$$

If we add all three equations together, we will get

$$
\begin{aligned}
& 2(J+O+T)=516 \\
& J+O+T=258
\end{aligned}
$$

Then, if we substitute the conditions of the problem into the last equation, we get

$$
\begin{aligned}
& J=18 \mathrm{~kg} \\
& O=72 \mathrm{~kg} \\
& T=168 \mathrm{~kg}
\end{aligned}
$$