Question

15 and 16 please help

Answer 1

15.
if he ordered  the same amount each month (x) and it is a whole number,
then
12*x=6150, and 
x =6150/12 should be a whole number
x=512.5
so 512.5 is not a whole number and the produce company does not agree

16.
16410/138≈118.91
because it not a whole number, she sells pieces for different prices