Question

Karen makes $5 per hour baby-sitting and $12 per hour giving music lessons. One weekend, she worked a total of 18 hours and made $139. How many hours did she spend baby-sitting?

Answer 1

This shall be funn
Let x = number of hours babysitting
Let y = number of hours giving lessons

From the information, you can write two equations

x + y = 18

5x + 12y = 139

Solve for x in the first equation :

x + y = 18

x = 18 - y

Put that value of x in the second equation and solve for y :

5x + 12y = 139

5(18 - y) + 12y = 139

90 - 5y + 12y = 139

90 + 7y = 139

7y = 49 . . . . . . . . . . . . . . [ subtracted 90 from both sides ]

y = 7 . . . . . . . . . . . . . . . .[ divided both sides by 7 ]

Now go back to the very first equation and put that value of y in and solve for x :

x + y = 18

x + 7 = 18

x = 11

She spent 11 hours babysitting.
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Check:

(11 hours x $5) + (7 hours x $12) = ($55 + $84) = $139

Answer 2

Did you understand that?

Answer 3

Ummm , kinda / not really :D

Answer 4

lols haha is there anything you need me to clarify?

Answer 5

This part :D
Put that value of x in the second equation and solve for y :

5x + 12y = 139

5(18 - y) + 12y = 139

90 - 5y + 12y = 139

90 + 7y = 139

7y = 49 . . . . . . . . . . . . . . [ subtracted 90 from both sides ]

y = 7 . . . . . . . . . . . . . . . .[ divided both sides by 7 ]