Answer:
There are 120 1st graders at Sierra Elementary School this year
Step-by-step explanation:
Let n represent the total number of 1st graders at Sierra Elementary School
Since 45% of all 1st graders at Sierra Elementary School are female students and this year there are 54 female 1st graders, 45% of n is equal to 54
→ n() = 54
→ 45n = 5400
→ n = 120