Problem with the comma between two independent clauses

[Huxley]

having a problem with the comma between two independent clauses.

i understand the simple sentences and when to use the comma.

like: She wanted to buy a new car, but she didn't have enough money to do so. (those kinds of phrases are easy because the subject is just after the conjunction.)

but when the subject is not just after the conjuction i am having trouble with.

i will try to find an exemple.

but can some one help me understand.

[Mister Micawber]

.
I would like to see a sample illustrating your problem, but if the subject is the same for both clauses, hence omitted in the second, then no comma:

She wanted to buy a car but didn't have enough money.
.
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Native English teacher at Mister Micawber's

[Huxley]

okay, here are some exemple in dialog.

1."You can plant whatever you'd like ( ) but first you have to remove all the rocks from it."

(i think what is confusing me is the 'but first' if it was 'but you' then i'd know what to do.)

2. "I lost hope in my old age ( ) but now it has finaly arrived."

[Pamela]

Hi Huxley,

That is how I'm analysing your examples:
first is not the subject but an adverb

"You can plant whatever you'd like ( ) but first you have to remove all the rocks from it (to my mind, two clauses are closely related and don’t need to be separated, the actions 'to remove' and 'plant' refer to the doer who is to perform the both actions).

[Yankee]

"I lost hope in my old age, but now it has finally arrived."
Another 'L' is needed, ;) however, with or without a comma, I find the sentence odd. :?
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"Nearly all men can stand adversity, but if you want to test a man's character, give him power." ~ Abraham Lincoln

[Pamela]

[Huxley]

i still don't understand it. about the commas just before two indenpendent clauses.

1."You can plant whatever you'd like ( ) but first you have to remove all the rocks from it."

if it was :"You can plant whatever you'd like ( ) but you have to remove all the rocks from it." then it would be easy -- place a comma.

Who has to remove all the rocks? "you"

can someone explain to about the phrases comma between the two independent clause. when the subject of the second clause is not just after the conjuntion.