100. 5 oxen and 2 sheep cost 10 taels, while 2 oxen and 8 sheep cost 8 taels. How much does each ox and each sheep cost separately?

Note. All three problems are from the treatise "Nine Sections on the Mathematical Art."

From the treatise "Nine Sections on the Art of Calculation."
100. We form the system of equations:

$$
5 x+2 y=10 ; 2 x+8 y=8
$$

A sheep costs $1 \frac{7}{9}$ tael, a goat $\frac{5}{9}$ tael

98

The treatise "Nine Chapters on the Art of Calculation" presents a commentary written in the mid-13th century on an older treatise (early 8th century) "Tian Li Shu".