To find the value of [tex]\(x\)[/tex] when [tex]\( f(x) = 9 \)[/tex], we start with the given function [tex]\( f(x) = 8x - 15 \)[/tex].
We are given that [tex]\( f(x) = 9 \)[/tex]. So, we set up the equation:
[tex]\[ 8x - 15 = 9 \][/tex]
Next, we need to solve this equation for [tex]\( x \)[/tex]:
1. Start by isolating the term with [tex]\( x \)[/tex]:
[tex]\[ 8x - 15 = 9 \][/tex]
2. Add 15 to both sides of the equation to get rid of the constant on the left side:
[tex]\[ 8x - 15 + 15 = 9 + 15 \][/tex]
This simplifies to:
[tex]\[ 8x = 24 \][/tex]
3. Now, divide both sides by 8 to solve for [tex]\( x \)[/tex]:
[tex]\[ x = \frac{24}{8} \][/tex]
Which simplifies further to:
[tex]\[ x = 3 \][/tex]
So, the value of [tex]\( x \)[/tex] when [tex]\( f(x) = 9 \)[/tex] is [tex]\( x = 3 \)[/tex].
Therefore, the correct answer is:
[tex]\[ \boxed{3} \][/tex]
