Final answer:
To solve for x when y = -9 in the equation y = (7/10)x + 7, after calculating, none of the listed options match the correct value of x. The correct x value is approximately -22.857, which is not included in the given choices.
Step-by-step explanation:
To find the input (x) that yields an output (y) of -9 in the equation y = (7/10)x + 7, we substitute -9 for y and solve for x:
-9 = (7/10)x + 7
First, we subtract 7 from both sides:
-9 - 7 = (7/10)x
-16 = (7/10)x
Next, we multiply both sides by 10/7 to isolate x:
(10/7) * (-16) = x
x = -160/7
x = -22.857...
Therefore, none of the given options (a. x = -20, b. x = -10, c. x = -14, d. x = -17) are correct. So there must have been an error, or the correct option isn't provided in the list.