1 Multiply the numerator of the left-hand fraction by the denominator of the right-hand fraction. Let's say you're working with the equation 2/x = 10/13. Now, multiply 2 by 13. 2 x 13 = 26.
2 Multiply the numerator of the right-hand fraction by the denominator of the left-hand fraction. Now multiply x by 10. x * 10 = 10x. You can cross multiply in this direction first; it really doesn't matter as long as you multiply both numerators by the denominators diagonal from them.
3 Set the two products equal to each other. Just set 26 equal to 10x. 26 = 10x. It doesn't matter which number you list first; since they're equal, you can swap them from one side of the equation to the other with impunity, as long as you treat each term as a whole.
*So if you're trying to solve 2/x = 10/13 for x, you'd have 2 * 13 = x * 10, or 26 = 10x.2
4 Solve for the variable. Now that you're working with 26 = 10x, you can start by finding a common denominator and dividing both 26 and 10 by a number that divides evenly into both numbers. Since they are both even, you can divide them by 2; 26/2 = 13 and 10/2 = 5. You're left with 13 = 5x. Now, to isolate x, divide both sides of the equation by 5. So, 13/5 = 5/5, or 13/5 = x. If you'd like the answer in decimal form, you can start by dividing both sides of the equation by 10 to get 26/10 = 10/10, or 2.6 = x.