Question

how do I find a value of x that will make each proportion true??
12 = x
___ ___
16 20

and
8 = 14
__ ___
12 x

See previous post.

i still don't get it sorry

Cross multiply to find x.

Here's the first one; perhaps you can try the second one on your own.

12/16 = x/20

Take 12 * 20, which is 240. Take 16 * x, which is 16x. This is cross multiplying.

Therefore:
16x = 240

Divide both sides by 16 to solve for x.

You will find that x = 15

You can check by substituting 15 for x in your original problem.

12/16 = 15/20

This is a true statement, so you know the answer is correct.

I hope this is clearer.

Thanks for posting, MathGuru. Really good work.