Answer:
D: x = -18
Step-by-step explanation:
A good way to solve this it to input all options until you find the one that fits for both options.
Option A :
15 + 6 / 15 - 3 = 21 / 12 or 7/4
So this one doesn't work.
Option B :
10 + 6 / 10 - 3 = 16 / 7
So this one also doesn't work.
Option C:
3 + 6 / 3 - 3 = 9 / 0 which is 0 by the laws of dividing by zero.
This one also doesn't work leaving only one option.
Option D:
-18 + 6 / -18 - 3 = -12 / -21 or 4 / 7
And by solving we can find out we did our work correctly and get our answer.