one number is 3 more than twice another number. The sum of the two numbers is 18. what are the two numbers?

Question

one number is 3 more than twice another number. The sum of the two numbers is 18. what are the two numbers?

Answer 1

x=one number

y=another number

 

Since you have 2 variables, you need 2 equations:

 

x+y=18  (the sum of the 2 numbers=18)

x=2y+3  (one number is 3 more than twice another number)

 

Solve the first equation for x:

 

x=18-y

 

Substitute 18-y for x in the 2nd equation:

 

18-y=2y+3

18=3y+3

15=3y

5=y

 

So one of the numbers is 5.  Substitute 5 back into the 1st equation to get the other number:

 

x+5=18

x=13

 

CHECK:

 

By using the 2nd equation and substituting in for both x and y, I can discover if these 2 values make the equation true.  If the final answer is true, then my answers for x and y are correct:

 

x=2y+3

13=2*5+3

13=10+3

13=13