Antoine sleep 8 hours in a day
The answer is 20p. P represents the number of boxes she buys and 20 is how many pens are in each box.
Answer:

The solution of the system can be given as (5,-8).
Step-by-step explanation:
Given system of equations:


To solve the given system of equations:
Solution:
We will use substitution to solve the given system.
We will substitute the
values in terms of
from the equation
into the other equation to solve for 
Substituting
into
.
We have:

<em>Using distribution.</em>

<em>Combining like terms.</em>

Adding 6 both sides.


Dividing both sides by 3.

∴ 
<em>Plugging in
into
.</em>
We have,

∴ 
The solution of the system can be given as (5,-8).
First divide 3.5 by 2 which equals 1.75. Then do 1.75*3 which equals 5.25. So he drinks 5.25 liters in one hour.