Answer:
Notebook $1.8
Pen $0.3
Step-by-step explanation:
Let's call x the cost of one notebook and y the cost of one pen.
If John spent $10.80 on 5 notebooks and 6 pens, we can write the following equation:
5x + 6y = 10.80
In the same way, if Arena spent $8.40 on 4 notebooks and 4 pens, we get:
4x + 4y = 8.40
Now, we have the following system of equations:
5x + 6y = 10.80
4x + 4y = 8.40
Solving the second equation for y:
4x + 4y = 8.40
4x + 4y - 4x = 8.40 - 4x
4y = 8.40 - 4x
4y/4 = 8.40/4 - 4x/4
y = 2.1 - x
Then, substitute y = 2.1 - x on the first equation:
5x + 6y = 10.80
5x + 6(2.1 - x) = 10.80
Solve for x:
5x + 6(2.1) - 6(x) = 10.80
5x + 12.6 - 6x = 10.80
-x + 12.6 = 10.80
-x + 12.6 - 12.6 = 10.80 - 12.6
-x = -1.8
x = 1.8
Now, using the value of x, we get:
y = 2.1 - x
y = 2.1 - 1.8
y = 0.3
So, the cost of one notebook is $1.8 and the cost of one pen is $0.3