Question: What is an algebraic formula, and how do you find one unknown variable when the others are known?

Sample answer: A formula is an equation that shows the relationship among two or more variables. To find an unknown variable, substitute the known values into the formula, then use algebra to solve for the remaining variable. For example, in $d = rt$, if you know $r$ and $t$, multiply them to find $d$.

Key points:

• A formula is an equation relating two or more variables.
• Substitute the known values into the formula.
• Use algebra to solve for the remaining variable.
• Example: in $d = rt$, multiply $r$ and $t$ to find $d$.

Rubric: Full credit: correctly defines a formula as an equation relating two or more variables and clearly explains substituting known values and solving for the unknown. Partial credit: gives a correct definition or a correct solving method, but not both. No credit: neither the definition nor the method is correct.