Three consecutive numbers are x, x+1 and x+2.
Four times the first integer is 4x
The sum of the second and third is (x+1)+(x+2)=2x+3.
So, we have

Subtract 2x from both sides:

Divide both sides by 2:

So, you can't have three consecutive integers such that four times the first is 18 more than the sum of the other two: the three numbers would be 10.5, 11.5, 12.5.
In fact, you have

and

Your answer is C: c = 2.50 + 2.50n
To get this answer I looked at the possible answers and inserted the numbers from the chart to see which fit.
He drove 219.375 miles more on the fist day than the second day.
Part A: Explain why the x-coordinates of the points where the graphs of
the equations y = 4-x and y = 2x + 3 intersect are the solutions of the
equation
4-x = 2x + 3.
Because the point where the graphs intersect is a point that meets both rules (functions) y = 4 - x and y = 2x + 3 meaning that y from y = 4 - x equals y from 2x + 3 and also both x have the same value.
Part B: Make tables to find the solution to 4-x = 2x + 3. Take the integer values of x between -3 and 3.
x values 4 -x 2x + 3
-3 4-(-3)=7 2(-3)+3 =-3
-2 4-(-2)=6 2(-2)+3 =-1
-1 4-(-1)=5 2(-1)+3 = 1
0 4-0=4 2(0)+3 = 3
1 4-1=3 2(1)+3=5
2 4-2=2 2(2)+3 = 7
3 4-3=1 2(3)+3 = 9
The the solution is between x = 0 and x =1
Part C: How can you solve the equation 4-x = 2x + 3 graphically?
Draw in a same graph both functions y= 4 - x and y = 2x +3.
Then read the x-coordinates of the intersection point. That is the solution.