First, you need to put them in order
53kg, 55kg, 61kg, 61kg, 76kg, 91kg, 98kg, 105kg, 120kg
For mean, you add them all up and divide by the amount of numbers (9)
720/9 = 80
For median, you find the middle number (76kg)
For mode, you find the number that appears the most (61kg)
Mean: 80
Median: 76
Mode: 61
Answer:
Step-by-step explanation:
Given that a teacher gives a test to a large group of students. The results are closely approximated by a normal curve
mu =74 and sigma =8
A grade starts from 100-8 = 92nd percentile
Z score for 92nd percentile = 1.405
X score = 74+8(1.405) = 85.24
--------------------
B cut off is to next 16%
Hence C would start for scores below 100-(8+16) = 76%
76th percentile = 0.705*8+74 =79.64
X - Jack's age
y - Susan's age
Jack is 27 years older than Susan.

In 5 years he will be 4 times as old as she is.

The system of equations:

Jack is 31 years old and Susan is 4 years old.