50x^8 y^8/25x^4 y2 + 28x^7 y^6/14^3

50X^8Y^8/25X^4Y^2 + 28X^7Y^6/14^3 =

2X^4Y^6 + 28X^7Y^6/2744 =
2X^4Y^6 + X^7Y^6/98 =
Common denominator = 98:
(196X^4Y^6 + X^7Y^6)/98 =
(X^4Y^6(196 + X^3))/98.