Answer:
Explanation:
Comment
The question is since f(x) really means y, then when y = 9 what's x?
Solution
y = 2x - 4
y = 9
9 = 2x - 4 Add 4 to both sides
9+4 = 2x Combine
13 = 2x Divide both sides by 2
13/2 = 2x/2
6.5 = x
Do you mean what is f(X) when x is 3. f(3) = 2x - 4. So what is y when x = 3
y = 2x - 4 Substitute 3 for x
y = 2*3 - 4 Combine
y = 6 - 4
y = 2