Л-37

ОДНОЙ ЛЁВОЙ highly coll NPjnstrum Invar adv fixed WO

(to do sth. ) without difficulty, quite easily

just like that

without half trying (be able to do sth. ) with one hand tied behind one's back (with one's eyes closed).

Разве это задача! Я такие задачи одной левой решаю. Some problem! I can solve this kind of thing with one hand tied behind my back.