Answer
See below.
Work Step by Step
The mean of $n$ numbers is the sum of the numbers divided by $n$. The median of $n$ is the middle number of the numbers when they are in order (and the mean of the middle $2$ numbers if $n$ is even). The mode of $n$ numbers is the number or numbers that appear(s) most frequently.
Hence here the mean: $\frac{69+70+71+73+73+74+75+78+78+84}{10}=74.5$.
The median is the average of the middle two numbers in the sequence, $69, 70, 71, 73, 73,74, 75, 78,78, 84$, which is: $(73+74)/2=73.5$.
The mode is $73,78$.
