この問題を解くのに２時間かかった。

this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)

question (e.g. on a test); problem; problem (e.g. societal, political); question; issue; subject (e.g. of research); case; matter; question (i.e. doubt); public discussion; controversy; trouble; problem; inconvenience; difficulty

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to untie; to unfasten; to unwrap; to undo; to unbind; to unpack; to unsew; to unstitch; to solve; to work out; to answer; to dispel (misunderstanding, etc.); to clear up; to remove (suspicion); to appease; to dissolve (a contract); to cancel; to remove (a prohibition); to lift (a ban); to raise (a siege); to release (from duty); to relieve; to dismiss; to comb (out); to card; to untangle (hair)

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

two

time; hours

to suffer from