4> Directly proportional to r^2 means that if the rate is reduced by 1/2, the stopping distance will reduce by to 1/4, i.e. to 75 feet. If you need to work it out more fully:
d=k*r^2
300=k*60*60 =>k=1/12
d=(1/12)*30*30 => d=75
5> I am always uneasy answering questions like this. You are given an annual rate of interest. To me that means that the frequency of compounding is irrelevant...but I am never sure because banks often do things differently and question writers may mean different thing. That said:
amount in 6 years = 12000*(1.035)^6=14751.06
6> When x=0 (the x intercept), y=5; when y=0 (the y intercept), x=-3
7> The most secure way to find the slope of a straight line is to write it in standard form: y=mx+b.
In this case y=.2x-6. The slope is .2y
to get that rearrange the original equation by adding 5y to each side and then subtract 30 from each side to get
5y=x-30, then divide by 5: y=.2x-6.
The y intercept is x=30