Answer: The number is 974
Step-by-step explanation:
First, any 3 digit number can be written as:
N = a*100 + b*10 + c
Where a, b, and c are single-digit numbers.
a is the hundreds digit
b is the tens digit
c is the unit digit
We can write the clues as:
#1: a + b + c = 20
#2: b = a - 2
#3: c = a + b - 12
Then we have a system of equations:
a + b + c = 20
b = a - 2
c = a + b - 12
To solve this, we need to isolate one of the variables in one equation and then replace this in the other equations, we can see that b is already isolated in the second equation, then we can replace that in the first and third equations:
a + (a - 2) + c = 20
c = a + (a - 2) - 12
Now we can see that c is isolated in the second equation, then we can replace that in the first one to get:
a + (a - 2) + (a + (a - 2) - 12) = 20
Now we can solve this for a:
a + a - 2 + a + a -2 - 12 = 20
4*a - 16 = 20
4*a = 20 + 16
4*a = 36
a = 36/4 = 9
With this, we can find the values of b and c.
b = a - 2 = 9 - 2 = 7
c = a + b - 12 = 9 + 7 - 12 = 4
Then the 3-digit number is:
N = a*100 + b*10 + c = 9*100 + 7*10 + 4 = 974
N = 974
