<PRE><B>Question 1184033</B>
Sum of three numbers is 15.
 a + b + c = 15 
The second number is two less than the first number.
 b = a - 2
or we can rearrange and write it
a - b = 2
The sum of the first two numbers is twice the third number.
 a + b = 2c

Identify the three numbers.
:
Notice a + b is in 1st and 3rd equation, so in the 1st equation we can write it
2c + c = 15
3c = 15
c = 15/3
c = 5
In the 1st equation, replace c with 5
a + b + 5 = 15
a + b = 15 - 5
a + b = 10
Use elimination with rearranged equation
a + b = 10
a - b = 2
-----------addition eliminates b, find a
2a + 0 = 12
a = 12/2
a = 6
find b
6 + b = 10
b = 10 - 6
b = 4
:
:
Check: 6 + 4 + 5 = 15</PRE>