Question

1/x-3=3/x-5

Answer 1

Did you forget your Order of Operations?

I'm almost sure you mean 1/(x-3) = 3/(x-5)
That is NOT what you have written.

Answer 2

first cross multiply
1(x-5)=3(x-3)
expand the brackets
x-5=3x-9
collect the like terms
x-3x=-9+5
simplify further
-2x=-4
solve for x by dividing both sides by -2
x=2

Answer 3

"Cross Multiply" doesn't mean anything. Just learn to multiply. Really, that's all there is to it.