Chiu Chang Suann Jing/Examples/Example 4

Example of Problem from

 * If $5$ oxen and $2$ sheep together cost $10$ taels of gold,
 * and $2$ oxen and $5$ sheep together cost $8$ taels,
 * what are the prices of oxen and sheep respectively?

Solution
An ox costs $1 \frac {11} {21}$ tael.

A sheep costs $\frac {20} {21}$ tael.

It would appear that the numbers for the problem were chosen with no thought to the convenience or plausibility of the answer.

Proof
Let $x$ be the price per ox.

Let $y$ be the price per sheep.

Then: