Question

How do you solve `\frac { 5} { 15} = \frac { x } { 75}`?

Answer 1

`x = 25`

Explanation:

You multiply BOTH sides of the equation with 75 and 15 :

`75 * 5 = 15 * x`

So now you divide BOTH sides with 15 and get :

`x = (75*5)/15`

Which gives the answer above.

I am totally stressing that you have to do the operations mentioned ( multiplication and division) to BOTH sides, as then and only then the equality sign will still hold true. In school they teach to just cross multiply which yields the same equation, but its not clear why you can do that. Now it should be ;)