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

Let the number of hours she spent in baby- sitting is x

and the number of hours she spent in music lessons is y.

Now, we have been given that she worked a total of 18 hours. Hence, we have

$x+y=18\\ y=18-x...............................(1)$

And she made $139. Thus, we have

$5x+12y=139..............................(2)$

Substituting the value of y from equation 1 in 2, we get

$5x+12(18-x)=139\\ 5x+216-12x=139\\ -7x=-77\\ x=11$

Therefore, she spent 11 hours in baby-sitting.