8/18 = x/225

Question

I don't understand :(

Answer 1

try something simple, like

3 = x/2

You want x all alone, so get rid of that pesky fraction. Since 2/2 = 1, multiply both sides by 2 and you get

3*2 = x/2 * 2
6 = x

Now, for your problem:

8/18 = x/225
You can clear the fraction on the left by multiplying by 18.

8/18 * 18 = x/225 * 18
8 = 18x/225
Now you want x all alone, so multiply by 225 to get

8*225 = 18x/225 * 225
1800 = 18x
Now divide by the a8 to get
100 = x

Of course, you don't have to clear both fractions, just the x/225:

8/18 * 225 = x
1800/18 = x
100 = x

Answer 2

http://www.mathsisfun.com/algebra/cross-multiply.html