Let X = the 29% alloy and Y = the 60% alloy.
They want a total of 80kg, so you have X +Y = 80
Rewrite that to get X = 80-Y
You also want 0.20X + 0.60Y = 0.52(80)
Replace X with 80-y:
0.20(80-y) + 0.60y = 0.52(80)
Simplify:
16 - 0.20y + 0.60y = 41.6
Combine like terms:
16 +0.40y = 41.6
Subtract 16 from each side:
0.40y = 25.6
Divide both sides by 0.40
y = 25.6 / 0.40
y = 64
Now you have Y replace y with 80 in X = 80-Y
X = 80 - 64
X = 16
They need 64 Kg of the 60% alloy and 16 Kg of the 20% alloy.
Formula:
V = 1/3 * pi * r^2 * h
Plug in what we know:
V = 1/3 * 3.14 * 3^2 * 4
V = 37.68cm^3
So the volume is 37.68cm^3 which rounds to 37.7cm^3.
I'm assuming you're looking for the dimensions of the plot. I'm going with that. ;) If the length of the plot is 5 meters longer than the width, then L = w + 5. The area for a rectangle is L*w, and we have an area value of 20,000 so our formula is 20000=(w+5)(w) and

. We will bring the 20,000 over by subtraction and set the polynomial equal to 0 to factor and solve for w.

Solving for w we get values of w=138.9 and -143.9. Of course the 2 things in math that will never EVER be negative are time and distance/length, so -143.9 is out. Our width is 138.9 and the length is 138.9 + 5 so the length is 143.9. And there you go! Hope that's what you needed!
With each gallon you need 11 gallons with 2 parts red 9 parts yellow and since 11x4= 44 you need to do this 4 times
4x2(red)= 8
4x9(yellow)=36
36+8=44
basically 8 gallons of red
i hope this made sense