The system of equations is x + y = 85 and 7/20x+2/5y=31
To eliminate the x-variable from the equations, you can multiply the equation with the fractions by 20 and multiply the other equation by -7.
B-She used 60 minutes for calling and 25 minutes for data.

Step-by-step explanation:

It is always a good idea to start by defining variables in such a problem. Here, we can let x represent the number of calling minutes, and y represent the number of data minutes. The the total number of minutes used is ...

x + y = 85

The total of charges is the sum of the products of charge per minute and minutes used:

7/20x + 2/5y = 31.00

We can eliminate the x-variable in these equations by multiplying the first by -7 and the second by 20, then adding the result.

-7(x +y) +20(7/20x +2/5y) = -7(85) +20(31)

-7x -7y +7x +8y = -595 +620 . . . . eliminate parentheses

y = 25 . . . . . . . . simplify

Then the value of x is

x = 85 -y = 85 -25

x = 60

7 0

3 years ago

Read 2 more answers

What is a detailed example of simple interest?

Sonbull [250]

Answer:

Car loans, amortized monthly, and retailer installment loans, also calculated monthly, are examples of simple interest; as the loan balance dips with each monthly payment, so does the interest. Certificates of deposit (CDs) pay a specific amount in interest on a set date, representing simple interest

5 0

3 years ago

Use the replacement set {3, 4, 9} to find the solution of the equation below. 3n−18=9

Mrac [35]

Answer:

$n=9$