Chelsea works two jobs to make money for her upcoming mission trip in the summer. She washes cars and babysits. She worked a total of 20 hours last week. She worked 3 times as many hours babysitting as she did washing cars. If [tex]x[/tex] is the number of hours she spends washing cars and [tex]y[/tex] is the number of hours she spends babysitting, how many hours did Chelsea spend babysitting last week?

Chelsea spent 15 hours babysitting last week. We found this by setting x as the hours spent washing cars and y as hours spent babysitting, using the equations x + y = 20 and y = 3x, and solving for x and y.

Explanation:

Let x be the number of hours Chelsea spends washing cars and let y be the number of hours she spends babysitting. Chelsea worked a total of 20 hours last week and spent 3 times as many hours babysitting as she did washing cars. This gives us two equations to solve for x and y:

x + y = 20 (total hours worked)

y = 3x (three times as many hours babysitting as car washing)

Substituting the second equation into the first, we have:

x + 3x = 20

4x = 20

x = 5

Now that we've found the number of hours spent washing cars (x = 5), we can use the second equation to find y:

y = 3 × 5

y = 15

Hence, Chelsea spent 15 hours babysitting last week.