Well, it's 40/4 for one minute, or 10 for one minute. You want 36 mins, so you multiply by the square root (6), to get $60, to which you also add the $90 for the lesson (result is $150)
Midpoint Formula: (

,

)
Midpoint = (

,

)
Midpoint = (

,

)
Midpoint = (

, -4)
So, the midpoint of the endpoints (-4,-3) and (7,-5) is (

, -4).
Have a nice day! ♪
4.5(8 - x) + 36 = 102 - 2.5(3x + 24)
36 - 4.5x + 36 = 102 - 7.5x - 60
72 - 4.5x = 42 - 7.5x
-4.5x + 7.5x = 42 - 72
3x = - 30
x = -30/3
x = -10 <===
Hope this helps!