how to solve this equation

Question

4/x = (√7 -1)/4

Answer 1

4/x = (√7 -1)/4

This can be considered a proportion; you can invert each side to get

x/4 = 4/(√7 - 1)  assuming that the square root's radicand is just 7, of course)

Now muliply both sides by 4 and you have the answer. If you wish to rationalize the denominator, that's OK, too.

Answer 2

Or you can cross-multiply.

 

x(√7 - 1) = 16

 

 

Now you can solve for x.  Since I don't know what part is under your square-root, as I noted in my comment, I will leave it as is and let you complete the rest.