Part A: First, list multiples for each number. The multiples of 5 are: 5, 10, 15, 20, 25 30, 35, 40, 45, 50, 55, 60, etc. The multiples of 12 are: 12, 24, 36,48, 60, etc. The least common multiple is the first common multiple between the two, in this case being 60. The LCM of 5 and 12 is 60.
Part B: SImilar to above, list all factors for each number. 72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72. 81: 1, 3, 9, 27, and 81. The greatest common factor is the highest common number, 9 in this case. The GCF of 72 and 81 is 9.
Part C: To rewrite, we need to take out the 9 by dividing. 72/9 is 8. 81/9 is 9. Therefore, we would get 9(8+9), to equal 153. Your answer here is 9( 8 + 9 ). Hope this helped!
Answer: He read 40% of the total time.
Step-by-step explanation:
As per given,
Total time he spent = 2 +1+2 = 5 hours
Number of hours he spent on reading = 2 hours
The percent of the total time he read = 

i.e. The percent of the total time he read = 40%
Hence, he read 40% of the total time.
9 = 1 + 8x - 8 = 8x - 7
8x = 9 + 7 = 16
x = 16/8 = 2
x = 2.