Suspecting that his parents are going to give him $1,300 continually you would solve like this
$120,000-$100= $19,900
$19,900/$1,300= 92.23
92.23 is the amount of $1,300 donations it would take from his parents, so if he was getting $1,300 month it would take 92.23 months
6 subsets are possible, but the number of subsets depends on the problem
If the battery was used for 11 hours, then the value of x we use is 11
Subtitute x with 11 in the equation
y = 100 - 8.9x
y = 100 - 8.9(11)
y = 100 - 97.9
y = 2.1
The remaining power is 2.1%
the answer is option b