Answer :
[tex]\text{21 + m = 66}[/tex]Explanation:
The sum of 21 and Mabel's score is 66:
This means 21 was added to Mabel's score to give 66
let Mabel's score = m
21 + Mabel's score = 66
In the from equation:
[tex]\text{21 + m = 66}[/tex]