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.
Keywords: average, division
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Let x = number of 5 cent coins.
Then there are (x+2) 10 cent coins.
Let y = 20 cent coins.
Total coins: x+(x+2)+y = 30
2x+y=28
y = 28-2x (1)
Total value: 0.05x + 0.1(x+2) + 0.2y = 3.80
0.15x + 0.2y + 0.2 = 3.80
0.15x + 0.2y = 3.60 (2)
Substitute (1) into (2).
0.15x + 0.2(28-2x) = 3.60
-0.25x + 5.60 = 3.60
2.00 = 0.25x
8 = x
From (1), obtain y = 28 - 2(8) = 12
Answer: (x+2) = 8+2 = 10
Louise has 10 10-cent coins
31°
Angles in the same segment are similar.
I'm not too sure how to explain, but in a circle when two "triangles" are formed from two same points on the circumference, the angle of the vertexes formed are the same (like in the picture)
3x - 12 = -5 plus 12
3x-12 +12 = -5+12
3x = 7 devision by 3
3x/3 = 7/3
x= 2,3333333333 =~ 2,3
2.75 times 60 equals 165
Answer: 165 inches, or 13 feet 9 inches