525.
1) m +1/n =(mn +1)/n
2) x/y -x =(x -xy)/y
3) (a² +b)/a -a =(a²+b -a²)/a =b/a
4) a -(ab -a)/b =(ab -(ab-a)/b =(ab -ab +a)/b =a/b
5) (2a²b -b)/a -ab =(2a²b -b -a²b)/a =(a²b -b)/a
6) a -(b/x) -(a/x²) =(ax² -bx -a)/x²
7) 5 -(1/x) -(1/y) =(5xy -y -x)/xy
8) a -(a-1)/2 +(a-2)/3 =(6a -3(a-1) +2(a-2))/6 =(6a -3a +3+2a -4)/6 =(5a -1)/6