the sum of two numbers is 21. the first number is twice the second number. What are the numbers

Question

thats all there is 

Answer 1

The numbers are 7 & 14.

n(2) + n = 21

3n = 21

n=7

 

7(2) + n = 21

14 + n = 21

n = 21 - 14

n = 7

 

7+7 or 7*2 = 14

Answer 2

Let x be the second number.  The first number is twice the second number, or 2x. Their sum is 21:

 

x + 2x = 21

3x = 21

x = 7

 

The other number is 2x =2*7 = 14

Answer 3

call your numbers "n" and "2 times n"

 

when you add them up, you get that 3 n's added together is 21

 

so if 3n is 21, one of those n's must be...

 

7, which would make the other one...

 

14.

 

Hope this helps.

 

Matt in NY