The sum of five consecutive numbers is 20. What is the sum of first three consecutive numbers ?

The correct option is 9.

Let's solve the problem step-by-step to find the sum of the first three consecutive numbers.

Step 1: Define the consecutive numbers
Let the five consecutive numbers be represented as:
$x$, $x+1$, $x+2$, $x+3$, and $x+4$.

Step 2: Set up the equation based on the given information
We are given that the sum of these five consecutive numbers is 20.
$\left(x\right)+(x+1)+(x+2)+(x+3)+(x+4)=20$

Step 3: Simplify and solve for $x$
Combine the like terms on the left side of the equation:
$5x+10=20$

Subtract 10 from both sides:
$5x=20-10$
$5x=10$

Divide by 5:
$x=2$

So, the five consecutive numbers are 2, 3, 4, 5, and 6.

Step 4: Find the sum of the first three consecutive numbers
The first three consecutive numbers are:
$x=2$
$x+1=3$
$x+2=4$

Now, calculate their sum:
$2+3+4=9$

Therefore, the sum of the first three consecutive numbers is 9.