Question 5278
Since you are looking for two unknowns (x = cost of call and y = hourly rate), it seems reasonable to expect to require two equations to solve the problem.
Let's set up the required equations from the given information:

1) x + 12y = $470   The cost of the call (x) + 12 hrs @ $y per hour is $470.
2) x +  5y = $225   The cost of the call (x) +  5 hrs @ $y per hour is $225.

Rewrite equation 1):  x = $470 - 12y and substitute into equation 2).

2a) ($470 - 12y) + 5y = $225  Simplify and solve for y, the hourly rate.

$470 - 7y = $225 Subtract $225 from both sides.
$245 - 7y = 0  Add 7y to both sides.
$245 = 7y Divide both sides by 7.
$35 = y  This is Mr. Ranger's hourly rate.

To find the cost of the call, x:

x = $470 - 12y
x = $470 - 12($35)
x = $470 - $420
x = $50 This is Mr. Ranger's cost of the call.

The equation that represents his earnings can now be written as:

E = $50 + $35(y)  Where: y is the number of hours spent doing the job.

Verification is left as an exercise for the student.