I can't really draw a trinagle on here so ill explain it!
A trinagle and it has 3 sides a,b,c,
A has no number
B says 13
C says 17
I have 2 find the length on side a
How do you figure it out do you add all the sides?
So it side a will -30?

I thought you said you would post in good English, not texting (which is forbidden on this site).

State the problem as it is on your worksheet or in your book. Your post is nearly unreadable.

Do you know the formulas for finding the side of a triangle?

It's a picture in the book and I don't no how to make a picture on here

Depends on the shape of the triangle. I am guessing that it's a right triangle, so the angle between sides 'a' and 'b' is 90 degrees,and 'c' is the hypotenuse - is that correct? If so you should use the Pythagorian Theorem, which says a^2 + b^2 = c^2. Here you would plug in values for 'b' and 'c' and solve for 'a.'

If the triangle is not a right triangle post back with more info about its shape.

"no" is spelled "know"

Is it a right triangle?

Yes it is

What's the -30?

What I think the answer is
I added all the sides

Why negative?

oh whoops that was a mistake it was meant to be =

Back up.

What is b squared? C squared?

What ever I got it but thanks for your time and pactince! :)

What is your answer?