The angles are supplementary, therefore totaling them at 180°.
And because I'm bored, I'll solve for x for you!
(x + 25) + (9x + 10) = 180
10x + 35 = 180
Subtract 35 from both sides.
10x = 145
Divide by 10 on both sides.
x = 14.5
First, we solve for the number of minutes in 7 and 3/5 hours by multiplying the number by 60 giving us,
(7 + 3/5) x (60) = 456 minutes
Spending 30 minutes for lunch will leave her with 426 minutes. Then, spending 42 minutes for switching of classes will finally give her 414 minutes.
We then divide this value by 6 (for her 6 classes) giving us 69 minutes. Thus, each class is 69 minutes long.
