This is very easy all u need to do is; 16-x/x=15/x+1, 16(x+1)-x(x+1)=15x , 16x+16-x2-x=15x, 16x-x-x2+16=15x, then 15x will get cancelled on both the sides and u are left with , -x2+16=0 , -x2=-16, x=4 (because underoot of 16 is 4) and x2 here is x square. Hope this helps!