There are three pumps P, Q and R with a tank. P. Q and R simultaneously can fill the tank in 5 hours. Again P and Q simultaneously can fill the tank in 7 hours. Then how many hours R need to fill the tank alone?

$Let, the company must sell x number of Frisbee to make break even.$

$According to question$

$7x = 10000 + 2x$

$= 7x - 2x = 10000$

$= 5x = 10000$

$\therefore x\frac{10000}{5}=2000$

The company must sell 2,000 Frisbee to make break even.

$Let, x be the maximum number of two points.$

According to question

$2x + (2 \times 3) = 26$

$= 2x + 6 = 26$

$= 2x = 26 - 6 = 20$

$\therefore x=\frac{20}{2}=10$

$Let, x be the total number of students in each class.$

$\therefore 10x will be the number of total students$

$Here, number of absent in 3 class = x-\frac{x}{2}=\frac{x}{2}$

$Number of absent in 5 class=x-\frac{3x}{4}=\frac{4x-3x}{4}=\frac{x}{4}$

$\therefore Number of absent in 2 class=\frac{x}{6}$

$$\begin{gathered} According to question \\ (3\times \frac{x}{2})+(5\times \frac{x}{4})+(2\times \frac{x}{6})=74 \\ =\frac{3x}{2}+\frac{5x}{4}+\frac{x}{3}=74 \\ =\frac{18x+15x+4x}{12}=74 \\ =37x=74\times 12 \\ \therefore x=\frac{74\times 12}{37}=24 \\ Hence, total students = 10 * 24 = 240 \end{gathered}$$