Maria has a total of 60 minutes to study.
She spent 18 minutes reading her notes and 35 minutes doing her study guide practice.
To find out how many minutes she has remaining, we first add the time she spent on both activities:
\[ 18 \text{ minutes} + 35 \text{ minutes} = 53 \text{ minutes} \]
Next, we subtract this total from her initial 60 minutes:
\[ 60 \text{ minutes} - 53 \text{ minutes} = 7 \text{ minutes} \]
Therefore, Maria has 7 minutes remaining for a break.