Answer:
The number of different lab groups possible is 84.
Step-by-step explanation:
<u>Given</u>:
A class consists of 5 engineers and 4 non-engineers.
A lab groups of 3 are to be formed of these 9 students.
The problem can be solved using combinations.
Combinations is the number of ways to select <em>k</em> items from a group of <em>n</em> items without replacement. The order of the arrangement does not matter in combinations.
The combination of <em>k</em> items from <em>n</em> items is: 
Compute the number of different lab groups possible as follows:
The number of ways of selecting 3 students from 9 is = 

Thus, the number of different lab groups possible is 84.
A24 = 141,
using equation,
an = a1 + (n-1)d,
a8 = a + 7d = 45
a16 = a + 15d = 93
solve simultaneously for values a and d, where a = 3, and d = 6.
therefore, inserting values into a24 eqn, where
a24 = 3 + (24-1)(6) = 141.