SOLUTION: How do you do this problem? "Phone and water bills together cost a company $790 for December. If the phone cost four times as much as the water, how much was each utility? How do y

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: How do you do this problem? "Phone and water bills together cost a company $790 for December. If the phone cost four times as much as the water, how much was each utility? How do y      Log On


   

Question 145947This question is from textbook Algebra For college students
: How do you do this problem? "Phone and water bills together cost a company $790 for December. If the phone cost four times as much as the water, how much was each utility? How do you make it an algebraic expression that I can work through? Please help! Thank you!
This question is from textbook Algebra For college students

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = phone cost
Let y = water cost
:
Write an equation for each statement:
"Phone and water bills together cost a company $790 for December."
x + y = 790
:
" If the phone cost four times as much as the water,"
x = 4y
:
how much was each utility?
:
Using the 1st equation; x + y = 790, substitute 4y for x
4y + y = 790
5y = 790
y = 790%2F5
y = $158 is the water bill
:
Using x = 4y, substitute 158 for y
x = 4(158)
x = $632 is the phone bill
:
:
Check 158 + 632 = 790; confirms our solutions