Question

5(wx-v)=9(x+v) make x the subject

Answer 1

Expand the brackets first
5(wx-v) = 9(x + v) 
5wx - 5v = 9x + 9v

Get all x's on one side and everything on on the other side
9x - 5wx = 9v + 5v

factorise out the x
x(9-5w) = 14v

then divide by 9-5w
x = 14v/(9-5w)

Answer 2

$5(wx-v)=9(x+v)\\ 5wx-5v=9x+9v\\ 5wx-9x=14v\\ x(5w-9)=14v\\ x=\frac{14v}{5w-9}$