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":

Commutative Property of Multiplication.
Answer:
18
Step-by-step explanation:
Delta math
Answer:
They took 4,180 minutes total to complete the course.
Step-by-step explanation:
The average time is given by the sum of each individual time of the members divided by the number of members on the group. So if we want to know the total time they took to complete the course we need to take the average and multiply it by the number of people in the group. So we have:
total time = average*number of members = 110*38 = 4180 minutes
They took 4,180 minutes total to complete the course.