## anonymous 5 years ago 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.

1. anonymous

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

2. anonymous

this is algebra 2

3. anonymous

if you set up equation I know how to solve

4. anonymous

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

5. anonymous

yes I can do

6. anonymous

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

7. anonymous

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

8. anonymous

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

9. anonymous

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

10. anonymous

given the key

11. anonymous

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

12. anonymous

thankyou haha

13. anonymous

robtobey how yu get number 10 and 5 ,

14. anonymous

the key for check answer not the given

15. anonymous

I'm working on a response.

16. anonymous

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

17. anonymous

{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.

18. anonymous

thanks

19. anonymous

You are welcome.