Answer:
Ever since my mother grew old, she often thought of all the things she did when she was young.
Step-by-step explanation:
In the given sentence structure, the blanks in the sentence propose an event of the past while the second blank is to be an adverb. This means that while the first blank will talk of the conditional past event, the second blank provides the modification or extra detail about the verb in the sentence.
As the first part of the sentence refers to a past event, we can put "ever since" in the blank. Ever since is used to refer to certain point in the past event leading up to the present,
Now, the next part of the sentence provides us what the mother used to do, with an added detail of her thinking about her younger days. The blank in the second part will be filled by the adverb "when", indicating the time when she was young.
Thus, the final sentence will be
Ever since my mother grew old, she often thought of all the things she did when she was young.