15%=3
5%=1
5(20)=100
1(20)=20
So, there are 20 students in the class.
(3,0)(0,4)
slope = (4 - 0) / (0 - 3) = -4/3
A perpendicular line will have a negative reciprocal slope. So our perpendicular line has a slope of 3/4
y = mx + b
slope(m) = 3/4
(-6,-5)....x = -6 and y = -5
now sub into the formula and find b, the y int
-5 = 3/4(-6) + b
-5 = -18/4 + b
-5 + 18/4 = b
-20/4 + 18/4 = b
-2/4 = b
so ur perpendicular line is : y = 3/4x - 2/4....or 3x - 4y = 2
and ur point (6,4) lies on the perpendicular line <===
Answer:
Tap A will take 2 hours and tap B will take 6 hours to fill the tank when turned on alone.
Step-by-step explanation:
Let tap B fills the pool alone in the time = x hours
So in one hour part of pool will be filled = 
Another tap A when turned on, it takes time to fill the pool = x-5 hours
So in one hour part of the same pool filled = 
Now both the taps A and B are turned on then time taken to fill the pool = 3 hours.
Part of the pool filled in one hour by both the taps = 
Now we form an equation
Part of pool filled in one hour by tap A + Part of pool filled in one hour by tap B = Part of pool filled in one hour by both the taps when turned on



3(x - 4) = x(x - 5)
x² -5x = 3x - 12
x² - 8x + 12 = 0
x² - 6x - 2x + 12 = 0
x(x - 6) - 2(x - 6) = 0
(x -2)(x - 6) = 0
x = 2, 6 hours
We will take higher value of x as x = 6 hours for tap B.
Time taken by tap A = 6 - 4 = 2 hours.
Therefore, Tap A will take 2 hours and tap B will take 6 hours to fill the tank when turned on alone.
The answer is 6 because 21+9=30 and 30-6=24 and 24 is the number of students in the class.