C. 2.4 x 10^6
D. 1.47 x 10^-3
I hope this helps !
Number of people < (should be smaller than or equal to but I don't have that button on my keyboard) (100-7) / 15.50
103/15.50 = 6.64516...
You can't have .645 of a person, so you must round down. Therefore, she can bring 6 people including herself.
Your multiplying by -4 each time
-1x-4=4
4x-4=-16
-16x-4=64