Here I am putting it in the picture.
15=-2(2t-1) -- expand brackets
15=-4t+2 -- subtract 2
13=-4t -- switch signs, best to have a positive variable
4t=-13
t=-13/4
She spent 17 hours tutoring
$210 = 7 hours
$20 x 10 hours = $200
$210 + $200 = $410
7 Hours + 10 Hours = 17 Hours