1To finish or conclude something; to get it over with (transitive).
宿題は夕方までに全部済ませておいてください。
Please finish all your homework by this evening.
会議は手短に済ますつもりだ。
I intend to keep the meeting brief / get the meeting over with quickly.
まず請求書の処理を済ませてから昼食に行こう。
Let's finish handling the invoices first, then go to lunch.
2To settle or pay off something (to clear a debt, pay a bill).
コーヒー代は私に払わせて、今すぐ済ましてください。
Let me pay for the coffee; settle it right now.
帰りにレジで勘定を済ました。
I paid the bill at the register on the way out.
3To manage without something or make do with a substitute; to get by with the minimum (often used as '〜で済ます').
朝ごはんはパン一枚で済ました。
I made do with a single slice of bread for breakfast.
今日は外食をせずに家で済ますつもりだ。
I plan to eat at home today and get by without dining out.
その修理は簡単な方法で済ませられる。
That repair can be taken care of with a simple method.