(37.5)(12.5)=x(15)
468.75=15x
x=31.25
she will have to work 31.25 hours in order to earn the same amount of money
300000*0.02=6000. So John gets 6000 dollars in commission.
Here, Sequence : -2, -6, -18, -54
Common Ratio = a₂/a₁ = -6/-2 = 3
As the expression is in negative sign, it's sequence will be -3ˣ
Where x = number of terms in the sequence [ By this rule, you can calculate the unknown nth number]
In short, Option C is your answer!!!!
Let me know, if you have some doubt.
= 1455
generate a few terms of the sequence using 
= 3n + 2
= ( 3 × 1) + 2 = 5
= (3 × 2) + 2 = 8
= (3 × 3 ) + 2 = 11
= (3 × 4 ) + 2 = 14
= ( 3 × 5 ) + 2 = 17
the terms are 5, 8, 11, 14, 17
these are the terms of an arithmetic sequence
sum to n terms is calculated using 
= 
[ 2a + (n-1)d]
where a is the first term and d the common difference
d = 8 - 5 = 11 - 8 = 14 - 11 = 3 and = 5
= 
[( 2 × 5) + (29 × 3) ]
= 15( 10 + 87) = 15 × 97 = 1455
