For this case we propose a system of equations.
We know that a dime equals 10 cents and a nickel equals 5 cents.
So:
x: Let the variable that represents the number of dimes
y: Let the variable that represents the number of nickels
According to the statement we have:

We multiply the first equation by -0.10:

We have the following equivalent system:

We add the equations:

So, Jeff has 3 nickels

Jeff has 12 dimes.
Answer:
12 dimes and 3 nickels
Answer: (3.5,-2)
Step-by-step explanation:
To solve this problem, all we have to do is plug in y=-2 into either equations from step one to find the coordinate. To make sure we have the right x-coordinate, let's plug in y for both equations.
4x-7y=28 [plug in y=-2]
4x-7(-2)=28 [multiply]
4x+14=28 [subtract both sides by 14]
4x=14 [divide both sides by 4]
x=3.5
------------------------------------------------------------------------------------------------------------
6x-5y=31 [plug in y=-2]
6x-5(-2)=31 [multiply]
6x+10=31 [subtract both sides by 10]
6x=21 [divide both sides by 6]
x=3.5
Now, we know the solution to the system is (3.5,-2).
I have the same problem here with a slight change in the given values:
radius is 2 & height of 6 indicates the bounding line is y = 3 x---> x = y / 3....
<span>thus the [ π radius ² thickness ] yields π (y² / 9 ) <span>dy ,</span> y in [ 0 , 6 ] for the volume... </span>
a Riemann sum is then : y_i = 0 + i [ 6 / n ] = 6 i / n , i = 1,2,3...n and do a right side sum
<span>π Σ { i = 1,2,3..n } [ 36 i² / 9 n² ] [ 6 / n ]
</span>
I hope my guide has come to your help. God bless and have a nice day ahead!