7L pour 3L, then pour 3L into 10L, and repeat twice. At this time, the 7L memory is1l.

Empty 3L, and then pour the remaining 7L into 3L.

Then 7L fills it up again. After filling it up, pour 7L into 3L, and the rest in 7L is 5L, 3L+10L and the rest is 5L.

This is probably the least step.