Question 288833
Generally, you should ask only one thing per question, however, these are all similar.

To solve a proportion, you can cross multiply.

{{{(3/x) = (x/3)}}} now, cross multiply

{{{x^2 = 9}}} now, take the square root of both sides

{{{x = 3}}} (plus and minus)

The other 2 solve in a very similar manner.