The equation below can be used to find the length of a foot or forearm when you know one or the other. (length of the foot) = 0.860 • (length of the forearm) + 3.302 if you let y = length of the foot and x = length of the forearm, this equation can be simplified to y = 0.860x + 3.302. using this equation, how long would the foot of a person be if his forearm was 17 inches long? what is the rate of change of the equation from part a? compare the equation from part a to your data. are they the same? which has a greater rate of change? why do you think the values are different? is the relation in your data a function? why or why not? could the equation in part a represent a function? why or why not? explain your answer.

This is child's play. 

So, basically:
Y=Length of foot
X= Length of your forearm. 
This is simple. Your equation is Y=0.860x + 3.302
So, if you have a forearm (x) that is 17 inches long, then plug in x as 17. This leaves you to evaluate for Y.
New equation: Y=0.860(17) +3.302
Work it out, you get: Y=14.62 + 3.302
Work that out, you get: Y= 17.922 inches long. 
And of course, Y is the foot.

So, your If the forearm is 17 inches long, then the foot is 17.922 inches long. Simple.

So, part 2:
Rate of change. Well, you need slope then, because that's the same thing.
Y=mx+b, Where m=slope
Your answer turns to be 0.860 inches per length of arm, for rate of change.

Skipping the data, as that's only something you'd know.

Yes, it is indeed a function. There can't be any exponents greater than 1 on the placeholder, and it's obviously not a straight line if you plug it in. 

So yeah, it's a function.

~Hope this helps m8