Question 990006
let the three number be a, b, c
:
write an equation for each statement
:
The second of three numbers is one less than the first.
b = a - 1
 The third number is five less than twice the second.
c = 2b - 5
 If the third number exceeds the first number by 12,
c = a + 12
:
find the three numbers 
In the 2nd equation, replace c with (a+12)
a + 12 = 2b - 5
a - b = -5 - 12
a - 2b = -17
replace b with (a-1)
a - 2(a-1) = -17
a - 2a + 2 = -17 
a - 2a = -17 - 2
-a = -19
a = 19
find 
b = 19 - 1
b = 18
find c
c = 19 + 12
c = 31
:
The three number: 19, 18, 31