1. The problem is to understand why the variable $x$ in part a is given the value 8.5 instead of the variable $a$. 2. Usually, in algebra or problem-solving, variables like $a$ and $x$ represent unknown values that can be assigned or solved for. 3. If the problem states $x=8.5$, it means that $x$ has been assigned or calculated to be 8.5 based on the conditions or equations given. 4. The variable $a$ might be a different parameter or constant in the problem, so $x$ and $a$ are not necessarily the same. 5. To clarify, if the problem or solution explicitly states $x=8.5$, it means $x$ is the value of interest, not $a$. 6. Without the full context or equations, the key point is that $x$ and $a$ are different variables, and $x$ has been found or set to 8.5. Final answer: $x=8.5$ because that is the value assigned or solved for $x$, not $a$.