Answer:
1. C(d)=0.69x+25.95
2. C(d)=0.69(57)+25.95
[0.69 times 57 is 39.33]
= 65.28 dollars
3. 136.3 miles
Explanation:
For the first question....
Since this is a function, we have to start with C(d). Even if you drive 0 miles, you still have to pay $25.95 just for renting the truck, so that is constant. For every mile you drive, you pay $0.69. Since we don't know how far anyone is going to drive, we will put 'x' as the amount of miles driven. The number of miles driven (x) multiplied by 0.69 will be the cost of that. The final function would be C(d)=0.69x+25.95.
For the second question....
We know the general function now, so driving 57 miles would mean substituting "x" for 57, and doing the multiplication (if necessary), 0.69 times 57 equals 39.33 (the dollar amount for driving 57 miles, not including the starting fee of 25.95)
Doing the math, you can get $65.28 (39.33+25.95).
For the third question...
If we have a budget, we know that C(d) is the amount of money spent, so we'll substitute the budget (120) for that. We'll solve the equation for x from there, and should get 136.3 miles (rounded to the nearest hundredth).
Hope this helps!