Solve x/42=3/7 using two different strategies.

You can solve this type of question two ways:

First cross multiply:
 x    =     3
42          7

(42)(3) = (7)(x)

This becomes :

126 = 7x

To solve for x divide both sides by 7 and you get x = 18

The other way to solve it is to think, what do I need to do to get x all by itself?

Since it's being divided by 42, you need to multiply each side of the equation by 42.

 42 *   x    =     3     * 42
         42          7

This leaves you with x = (42*3)/2
This simplifies to x = 18