Fourths, then b. Sorry if late.
Let:
x = Chemistry textbooks sold
y = Physics textbooks sold
The textbook store sold a combined total of 260, so:

The number of chemistry books sold was three times the number of physics textbooks sold, so:

Let:

Replace (2) into (1):

Replace the value of y into (2):
Answer: the first one
Step-by-step explanation: the number is 42 45 45 46 and 48 are all close together while the number 16 is off to the whole other side
Answer:
4????
Step-by-step explanation:
Answer:
193 in
Step-by-step explanation:
Volume of a triangular prism:
The volume of a triangular prism is the base area multiplied by the wedge, that is:

The base area is one half times the triangle base times it's height, so:

The wedge of cheese is 7 inches tall.
This means that 
The base of the cheese is shaped like a triangle with a base of 11 and a height of 5 inches.
This means that 
Volume:

Rounding, approximately 193 in.