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B.

Step-by-step explanation:

So, lets remember a few things first.

#1: The formula for finding the answer is A^2+B^2=C^2

#2: A is the opposite side, B is the adjacent side, and C is the hypotenouse side.

Now lets plug in what we already know, and see if we canf igure out the annswer:

A^2+12^2=13^2

Now I am going to stop us here. This is your equation that will find the answer. In your question, they use x^2, A^2 is a variable you can use instead. But looking at this, answer B and my equation I wrote above are exactly the same.

If you want, here is how I further solved it, this might give you a better grasp on what to do for future problems:

Ok, not  too bad, the A is the unkown value, which is the opposite side.

Now, how do we figure this out? Well, we just need to sovle for A.

To do this, lets clean up our equation by first sqauring all the values(except for the unkown):

A^2+144=169

Ok, that looks better, now lets just subtract the adjeacent side(b), which is 144, from the hypotenouse side(c), which is 169.

This will now look like:

A^2=25(169-144=25)

Ok, just one more step to go. Just square root both sides of the equation, this way, we will get ride of the ^2 on A(opposite side), and get A alone.

()=()

A=5

This is your answer.

is there any attachment? what are the equations?

relating to or denoting a system of numbers and arithmetic based on the number ten, tenth parts, and powers of ten.

step-by-step explanation: