Answer: 3
Step-by-step explanation:
The standard notation for a point (also called an ordered pair) is (x, y).
And the standard form of writing a function is:
y = f(x).
Where x is the "input" of the function, and y is the "output" of the function.
Then we can see that in the point (x, y)
The input is the first number, and the output is the second number.
Then for the point (3, 18), the fist number will be the input, then:
In the ordered pair (3, 18), the value that represents the input to a function is 3.
