Algebra-1

Question Analysis
The question tests the student's understanding of the definition and application of proportions. It requires the student to use cross-multiplication to solve for the unknown variable.

Key Concept Explanation
A proportion is an equation stating that two ratios are equal. The cross-multiplication rule states that in a proportion , the product of the means (b and c) is equal to the product of the extremes (a and d).

Step-by-step Solution
1. Start with the given proportion:
2. Apply the cross-multiplication rule: