The sum of three numbers is 12. The first number is twice the sum of the second and third. The third number is 5 less than the first. Find the number.
The key is: first is 8, second is 1, third is 3
This is complicated if you have to show your work and not just guess and check. Set up the equations first.

Question

anonymous · Answer

There aren't really equations. You just have to use logic. Use that Logic, process of elimination.. I'm not sure what level of math you are in though

anonymous · Answer

this is algebra 2

anonymous · Answer

if you set up equation I know how to solve

anonymous · Answer

You could maybe use probability. Are you learning about Cnr and Pnr?

anonymous · Answer

yes I can do

anonymous · Answer

I can solve you don't have to solve , you just  help me set up equation

anonymous · Answer

umm okay i'm not sure if this is right but

anonymous · Answer

figure out how many sums of 3 DIFFERENT (whole) numbers add up to 12. so 12*11*10

anonymous · Answer

so thats your total possibilities and now u can narrow it down

anonymous · Answer

given the key

anonymous · Answer

$$\{a+b+c=12,a=-10+2 a+2 b,c=a-5\} $$$$\{\{a\to 8,b\to 1,c\to 3\}\} $$

anonymous · Answer

thankyou haha

anonymous · Answer

robtobey how yu get number 10 and 5 ,

anonymous · Answer

the key for check answer not the given

anonymous · Answer

I'm working on a response.

anonymous · Answer

I still don't get ,how you get -10?

anonymous · Answer

{a + b + c = 12, a = 2 (b + c) , c = a - 5}
Replace c in the first two equations with (a-5)
{-5 + 2 a + b = 12, a = 2 (-5 + a + b)}
Expand the second equation above by multiplying through by 2
{-5 + 2 a + b == 12, a == -10 + 2 a + 2 b}
Solve the above two equations for a and b
Take the value of a and plug it into c = a - 5 to obtain the value of c
I hope I got this correct.

anonymous · Answer

thanks

anonymous · Answer

You are welcome.