A man carries a 10 kg sack of groceries in his arms with a force of 50 n as he walks forward a distance of 10 m how much work has he done

500 Joules.

To find this answer you need an equation. The equation is fairly simple. W=F*D "Work equals Force times Distance"

There are 50 Newtons over 10 meters as you said. So ...

500J = 50N * 10m