Issac drove the first three hours at 44 miles per hour.
Step-by-step explanation:
Given,
Average speed of Isaac = 49 mph
Let,
x be the speed during last three hours.
Speed during first three hours = 4x-172
Average = 

Multiplying both sides by 2

Dividing both sides by 5

Speed during last three hours = x = 54 mph
Speed during first three hours = 4x-172 = 4(54)-172 = 216-172 = 44 mph
Issac drove the first three hours at 44 miles per hour.
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85 + 95 = 180$
So 150 - 180 = -30$ so she is 30 dollars in debt.
Well 32 minutes is half of an hour so 8 miles would be half of the full x miles
so 8 x 2 would be 16
16 miles per hour
Simple interest formula:
Interest = P*R*N
P = principle amount
R = interest rate (in decimal)
N = number of time periods (in years)
Interest = 5000*0.05*4 = $1000