Answer:
Cost of one pencil: 
Cost of one eraser: 
Step-by-step explanation:
Let be "p" the cost in dollars of one pencil and "e" the cost in dollars of one eraser.
Based on the information given in the exercise, you can set up the following system of equations:

You can use the Elimination Method to solve the system of equations.
Multiply the first equation by -3 ad the second one by 4. Then add the equations and solve for "e":
{
Substitute the value of "e" into any original equation and solve for "p":

I have completed the 1st one and have attached it.
Function means no x value repepetes with a differnt y value
(x,y)
first numbers never repeat
first one, the x values repeat
2nd, x values rpeat
3rd, no repeat
4th, -3 repeats
answer is 3rd option
The correct answer is choice B.