Perfectly correct. Two quarters do make a half :)
D, Each x value has one and only one y value.; This is because if an x-value repeats itself then it is not a function. You can test this on a graph by drawing a vertical line on it. If the vertical line intercepts the line more than once anywhere on the graph, then it is not a function.
3(x - 25) < $100. We're not req'd to solve this.
1/3*4= 4/12
3/4*3= 9/12
Answer is 4/12 and 9/12.
It would be about 3.5 miles long so you chose 3 miles or 4 miles i would go with (4 miles)