This is the 7743rd most frequent Korean word.
하겠다고
"하겠다고" means "saying that (someone) will do."
Here, '하겠다고' communicates a statement of intention relayed in reported speech. It indicates someone else's intention to perform the action of exercising.
그는 내일 운동을 하겠다고 말했어요.
He said he would exercise tomorrow.
In this sentence, '가겠다고' conveys a reported decision or declared intention regarding their action to go downtown.
학생들이 시내로 가겠다고 결정을 내렸어요.
The students decided that they would go downtown.
'끝내겠다고' here expresses the reported promise or commitment to completing the work.