Question

The second of three numbers is 4 times the first number. The third number is 12 less than the first. Find the three numbers given that their sum is 42.

Answer 1

just forming a matrix

Answer 2

let the first number be x

second be y, third be z

Answer 3

y= 4x

z=x-12

x+y+z=42

Answer 4

solve etc

Answer 5

sub the first and second eqn into the third

Answer 6

6x -12 = 42

Answer 7

etc , its easy from now

Answer 8

6x=54

x= 9

Answer 9

y= 36

Answer 10

z=-3

Answer 11

let's call the numbers x, y, and z. We can turn the statements into equations:
1. y = 4x
2. z = x - 12
3. x + y + z = 42

Now we can put "4x" in place of "y" and "x - 12" in place of "z" in equation 3, because equations 1 and 2 tell us they are equivalent. Then we solve for x:

x + 4x + x - 12 = 42
6x - 12 = 42
6x = 54
x = 9

Plug x into the first 2 equations to solve for y and d:

y = 4(9)
y = 36

z = 9 - 12
z = -3

Answer 12

or "what elecengineer said." BTW, I'm also an electrical engineer. :-)