Answer:
11%
Explanation:
this is simple because there are 4 parts of the pie chart, and we are given 3. the one we don't know we will call x. Since its percents, we know that all of the percents will add up to 100, so we can write an equation.
45 + 23 + 21 + x = 100
to solve, you can subtract 45, 23, and 21 from both sides and you are left with x = 11 which is your solution for how many students had 3 or more absences.
hope it helps!