(Y-Y1)/(X-X1)
(-9-(-29))/(7-15)
20/-8
-2 1/2
The slope is -2 1/2
3 hours is 180 minutes.
She rested for 20 additional minutes, thus it will take her 200 minutes.

First, solve the parentheses:

Next, the exponential terms

Solve the multiplication:

Add and subtract:
Multiply the numerators and denominators together:
-24/150
Divide the numerator and denominator by 6:
-24 / 6 = -4
150 / 6 = 25
-4/25