Alan

(a)  40 pounds of alfalfa gives 40*0.2 = 8 pounds of protein.  60 pounds of wheat gives 60*0.15 = 9 pounds of protein so, in total, there are 8 + 9 = 17 pounds of proptein in the mixture.

(b).  Let A = pounds of alfalfa and W = pounds of wheat.

A + W = 1000    ...(1)  Total weight of mixture

0.2A + 0.15W = 0.17*1000    Total weight of protein 

0.2A +0.15W = 170   ...(2)

Multply (2) by 5

A + 0.75W = 850  or  A = 850 - 0.75W

Put this into (1)

850 - 0.75W + W = 1000   or 0.25W = 150  or  W = 600

Put this back into (1)   A + 600 = 1000  so A = 400

400 pounds of alfalfa and 600 pounds of wheat mids.

Thanks for pointing out the mistake guys - I've now corrected it.

have a look at http://web2.0calc.com/questions/math-help-ty and use the same method.

Have a look at http://web2.0calc.com/questions/math-help-ty and use the same method here.

Let C = number of bags of chips and S = number of sodas.

2.5*C + 0.5*S = 80           ...(1)

S = 5*C                            ...(2)

Replace S in (1) using (2)

2.5C + 0.5*5C = 80

2.5C + 2.5C = 80

5C = 80

C = 80/5 so C = 16

Put this back into (2)

S = 5*16 so S = 80

Vertcal velocity.  Use v^2 = u^2 + 2*a*s  where v = final vertical velocity, u = initial vertical velocity = (60000/3600)*sin(70°)  m/s ≈ 15.66 m/s,  a = -g = -9.8 m/s^2, s = 400m

v^2 = 15.66^2 - 2*9.8*400    (m/s)^2    so v  =  ...     you can finish this off

For the time use  v = u + a*t  where t is the time.

If (a + b)² = 49 then a + b = 7  or  a + b = -7

so b = 7 - a   (1)   or b = -7 - a  (2)

using (1):   a*(7 - a) = 10  so a² - 7a + 10 = 0   or (a - 5)(a - 2) = 0  so a = 5 (and b = 2) or a = 2 (and b = 5)

See if you can repeat the process using (2).

Edited to correct stupid misprint!

Just add up all three equations to get   3x + 3y + 3z = 51

Divide both sides by 3:

x + y + z = 17

sin^-1(3) means the angle whose sine is 3.  However, sine is always between -1 and +1, so sin^-1(3) doesn't exist.

Work is a form of energy transfer and so is measured in joules the same as energy.

The formula for kinetic energy is E = (1/2)m*v^2. Where E is energy, m is mass and v is velocity.

heureka beat me to it!