1. Let's clarify the problem: You are asking why the expression $d/10$ appears in step 3 of a solution. 2. Typically, $d/10$ means dividing the variable $d$ by 10, which could represent scaling, unit conversion, or part of a formula. 3. To understand why $d/10$ is used, we need to see the previous steps or the formula involved. 4. For example, if the problem involves finding a fraction or percentage of $d$, dividing by 10 could mean taking one-tenth of $d$. 5. Without the full context, the general rule is that dividing by 10 shifts the decimal point one place to the left, effectively scaling the value down by a factor of 10. 6. If you provide the full problem or previous steps, I can explain exactly why $d/10$ is step 3.