Step-by-step explanation:

multiply both sides by a - r

divide both sides by s

subtract a from both sides

invert the signs

Well I suppose it depends on how long you have in a day but...
with 30 people you can have it done in about 8hrs
but with 20 people you can have it done in about 12 hours
so my best guess would be anywhere between 20-30 people
Assuming you need an answer to question #7, here it is.
The sum of all angles inside a polygon depends on the number of sides it has. (n-2) x 180°, where n is the number of sides. Knowing there are 5 sides to the polygon, we can figure out the sum of its interior angles :
(5-2) x 180° = 3x180° = 540°
We know the values of the two right angles on the right side of the shape. They both are of 90° (aka right angle) and add up to 180°. This means that the other angles must make up the rest : 540° (Total) - 180° (right side) = 360° (total of angles A, B and C).
Now we need to make relations between these unknown angles.
1. A=B They were described as having the same size;
2. A=2C A and B were described as being twice as big as C, so we would need two times C to equal A;
3. A+B+C = 360° Which we figured out earlier.
Since B=A we can replace B in the third equation :
A+A+C = 360°
2A+C = 360°
We also know that A=2C :
2(2C)+C=360°
4C+C=360°
5C=360°
We solve for C :
C=72°
Now that we know the value of angle C, we can work our way up towards angles A and B.
A=2C
A=2(72°)
A=144°
B=A
B=144°
We can verify our values to see if it all makes sense.
Is A+B+C=360° still true?
144°+144°+72°=360°
360°=360°
Thus, angles A, B and C are respectively 144°, 144° and 72°.