1. \( x: 4=9: 12 \)

To solve for \( x \) in the proportion \( x: 4 = 9: 12 \), you cross-multiply. This gives you \( x \times 12 = 4 \times 9 \). Simplifying, you find \( x \times 12 = 36 \), which leads to \( x = 3 \). Voila! You’ve just uncovered the value of \( x \) with a little math magic! Proportions like this are not just academic; they find real-world applications in various fields, such as cooking and engineering. For instance, if a recipe requires ingredients in certain ratios, understanding proportions helps you scale everything up or down without ruining the dish, ensuring your culinary creations come out just right every time!