ElectricPavlov

e = mc^2  = (.001)(3 x 10^8)^2      1 x10^-3    *  9 x 10^16    =  9 x 10^13 joules

Here is a solution

17 16 15 14 13 12 11  9 8 7 5 5

Another

17 16 15 14 13 12 11 9 7  7 6 5

Let's first figure out how many tons 100 sccops is:

100 scoops  100 m3/scoop  1.5 ton/m3  = 15000 ton         15000ton / 40 ton/car = 375 cars

Oh yah,    another way   

  hmax = c - (b^2)/(4a)

hmax = 80 - (64^2)/(-64)

          = 80 + 64 = 144 feet  (STILL a wimpy rocket !)

I agree with Guest 2

It's an EQUALateral triangle , so by definition all of the sides are the same length...

So:

4x-y=7        solve for y= 4x-7

2x+3y=7   Substitute y= 4x-7 in here

2x + 3(4x-7)= 7

14x = 28    x= 2   so y = 1  

You can graph the quadratic to see the rocket's path....you will see it peaks out at 144 feet

Or, if you know how, you can take the DERIVATIVE of the quadratic (which results in an equation giving you the SLOPE of the original quadratic) and set = 0 (this would be when the rocket's path is at it's apex)   to find 't' ...then substitute this 't' into the original equation

Derivative = -32t + 64   = 0   results in 't' = 2 seconds

Substitute 't' = 2 into the original equation:

h = -16(2)^2 +64(2) + 80 =  144 feet max  (pretty wimpy rocket !)

Or, you can 'trial and error' it to find the 't' that gives you greatest 'h'

OK....How?   

       I thought you were going to post instructions because that is not a question.

Not sure what you are asking, but x= 3