To use cross-multiplication for solving proportions, just follow these simple steps:

Step 1: Know What Proportions Are

A proportion shows that two ratios are equal. It usually looks like this:

$$\frac{a}{b} = \frac{c}{d}$$

In this, $a$, $b$, $c$, and $d$ are numbers. Your job is to find one of these numbers.

Step 2: Set Up the Problem

First, figure out the values you need. For example, if you have:

$$\frac{3}{4} = \frac{x}{8}$$

Here, $3$ and $4$ form one ratio, and $x$ and $8$ make the other ratio.

Step 3: Cross-Multiply

Cross-multiplication means you multiply the top number of one ratio by the bottom number of the other ratio. In our example, you do:

$$3 \times 8 = 4 \times x$$

This gives you:

$$24 = 4x$$

Step 4: Find the Missing Number

Now, you can solve for $x$. Divide both sides by $4$:

$$x = \frac{24}{4} = 6$$

Step 5: Double-Check Your Answer

It’s always smart to check your work. Put $x$ back into the original proportion:

$$\frac{3}{4} = \frac{6}{8}$$

If you simplify $\frac{6}{8}$, you get $\frac{3}{4}$, so our answer is right!

Summary

Here’s a quick recap:

1. Understand what a proportion looks like.
2. Set up the problem correctly.
3. Cross-multiply the fractions.
4. Solve for the missing number.
5. Check your answer.

By following these steps, you’ll get better at solving proportions. Happy calculating!