你可能agree to一个东西，但是你不一定agree with它。
1.“agree to do sth”表示“同意做某事”
不定式 to do 含有“要去做......”的含义，所以，agree to do 就是同意去做什么事，例如：
What on earth had possessed her to agree to marry him?
You and I are going to have to agree to disagree then.
The undersigned buyers agree to pay a 5,000 pound deposit.
She agreed to have a swim with me. 她同意和我一起游个泳。
Did you agree to come with him? 你同意跟他一块去了吗？
当agree to中to作介词时，含义为：接受、认可，常常指并非出于主观愿望的“同意”，尤指不乐意或经过争论之后的同意（含有未必赞成的意思）；agree to后常接建议、计划、安排等如：
At last his wife agreed to the trip if he allowed her to go also.
Those who agree to this plan please put up their hands.
I cannot but agree to your decision.
The enemy is so desirous of peace that he will agree to any terms.
We will agree to disarming troops and leaving their weapons at military positions.
The management is understood to be very unwilling to agree to this request
I was forced to agree to it, but at heart I didn’t quite agree with it.
He said all that remained was to agree to a time and venue
2. agree with指出自主观愿望的“赞成、接受、同意”，如：
I don’t agree with a single word that you have said.
In many ways I agree with his statement. 多方考量，我同意他的说法。
The great majority of people seem to agree with this view.
As the author of the proposal I cannot agree with you.
I don't really agree with that.
I don't agree with you there.
I don't altogether agree with you.
I entirely agree with you.
I don't agree with spanking.
In his heart he knew they'd agree with his stand.
I completely agree with your recent editorial. 我完全同意你最近的社论。
Your account of the accident does not agree with hers.
His story agrees with the facts. 他的陈述与事实相符。
A verb must agree with its subject in person and number. 动词必须和它的主语在人称和数方面保持一致。
The weather doesn't agree with me.我没有适应这里的气候。
The food does not agree with me. 这食物对我不适合。
Hard work does not agree with him. 艰苦的工作对他不适宜。
The author can report other people's results which more or less agree with hers.
3. agree on表示：两方或多方就某事取得一致意见或达成协议；所以运用这个词组的时候，就必须是至少有双方或三方乃至多方才能一致意见或达成协议这个含义：
When did you last hear from Jay?
He phoned me this morning, and we agreed on a time and place to meet.
Can we agree on a date?
We rarely agree on what to do.
The two sides failed to agree on the wording of a final report
It took five months for the coalition to agree on and publish a medium-term
'I think we could agree on that one.' — 'Only just.'
He agreed on helping us. 他同意帮助我们。
注：与 agree to do sth 大致同义。所以上句也可说成：
He agreed to help us.