The only non-linear equation from your choices is the area of a circle as it is:
A=πr^2 and if you take the derivative of A you have:
dA/dr=2πr
So the rate of change changes as r changes, it is not constant thus the function has acceleration, so velocity changes.
This is in contrast to any linear equation which is of the form:
y=mx+b now taking the derivative you see that:
dy/dx=m, now m is a constant value, which means that there is no acceleration and the velocity remains constant.
The minimum score was 70.
On a box-and-whisker, the dot on the left end is the lowest value.
The first line on the left is the lower quartile.
The second line is the median.
The third line is the upper quartile.
And finally, the dot on right end is the highest value.
Hope I could help :)
When x=-1:

Ok that gives us a little more information.
If we implicitly differentiate with respect to t, from the very start, then we can apply our product rule, ya?

The right side is zero, derivative of a constant is zero.
Where x' is dx/dt and y' is dy/dt.
From here, plug in all the stuff you know:
y' = -3
x = -1
y = 4
and solve for x'.
Hope that helps!