I think I only know the answers to 4 and 5 :)
5 = 9a + 12b
4 = subtraction
Answer: a) Explicit formula :
b) Recursive formula :
and 
Step-by-step explanation:
Since we have given that
Number of grams of yeast in a culture dish initially = 9 grams
According to question, a certain culture of year increases by 50 % every three hours.
So, the explicit formula will be

And the recursive formula will be

Hence, a) Explicit formula : 
b) Recursive formula :
and 
Answer:
The answer is 17.15! Brainliest pls :D
3a, because both terms contain a, and 6 is divisible by 3
Divide 9 by 15.
9/15= 0.6
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I hope this helps!
~kaikers