1.75 Grams is what I got. Every 1 Milligram = 0.001 Gram.
Hope it helps :)
There are 60 minutes in an hour and percent means per one hundred so:
p/100=18/60
p=1800/60
p=30%
To answer this question we can propose the following equation:

Where:
x is the number of weeks elapsed.
d is the debt depending on the weeks.
Robert promised to pay at least $ 67 each week.
Therefore, after 5 weeks the debt of rober should be:


Then scenario A) is possible because
.
After 6 weeks:


Then scenario B) is possible because
.
After 7 weeks


Then scenario C) is possible because
.
After 8 weeks


So scenario D) is NOT possible because 
Finally the correct answer is option D.