Answer:
Your answer is D
Step-by-step explanation:
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1.7a + 0.3a = 0.8;
(1.7 + 0.3)a = 0.8;
2 x a = 0.8;
a = 0.8 ÷2;
a = 0.4;
You'll be using point slope form to solve this.
As the name suggests, you'll need the slope as well as a point. To find the slope use the slope formula: 
Plug in the points.

The slope of this line is 5.
Point slope form is y-y1 = m(x-x1), so plug in the slope and a point into this equation. I'll use (0,8).
y-(8) = 5(x-(0))
1. Write this out without parentheses.
y-8 = 5(x)
2. Multiply 5 and x.
y-8 = 5x
3. Add 8 to both sides.
y = 5x+8
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Answer is:
y = 5x+8
5 2/3 divided by 2 2/3 = 17/3 divided by 8/3 = 17/8 = 2 1/8 miles per hour
2 2/3 divided by 5 2/3 = 8/3 divided by 17/3 = 8/17 hours per mile