How many days will it take to seed 350 hectares with 2 tractors?

Tractors	Hectares	Days
3	400	5
2	350	\(x \)

As the number of tractors has decreased, we will require more time. Therefore, from the numbers in the first column, we create the fraction that is greater than 1 (i.e. \( \frac{3}{2} \))

As the number of hectares has decreased, we will require less time. Therefore, from the numbers in the second column, we create the fraction that is less than 1 (i.e. \( \frac{350}{400} \))

\begin{align} So \quad x & =\frac{3}{2}\ \times\ \frac{350}{400}\ \times\ 5 \\ \\ & = \frac{3}{2}\ \times\ \frac{7}{8}\ \times\ 5 \\ \\ & = \frac{105}{16} \\ \\ & = 6 \frac{9}{16}\ days \end{align}

How many tractors will be needed to seed 450 hectares in 1 day?

Tractors	Hectares	Days
3	400	5
\(x \)	450	1

As the number of hectares has increased, we will require more tractors. Therefore, from the numbers in the second column, we create the fraction that is greater than 1 (i.e. \( \frac{450}{400} \))

As the number of days has decreased, we will require more tractors. Therefore, from the numbers in the third column, we create the fraction that is greater than 1 (i.e. \( \frac{5}{1} \))

\begin{align} So \quad x & =\frac{450}{400}\ \times\ \frac{5}{1}\ \times\ 3 \\ \\ & = \frac{9}{8}\ \times\ \frac{5}{1}\ \times\ 3 \\ \\ & = \frac{135}{8} \\ \\ & = 16.875 \quad tractors \\ \end{align}

But as a part-tractor is nonsense, we need 17 tractors