IF you are solving for d:
isolate the D, do the opposite of PEMDAS.
-d/6 + 12 = -7
(subtract 12 from both sides)
-d/6 + 12 (-12) = -7 (-12)
-d/6 = -19
(multiply 6 to both sides)
-d/6(6) = -19(6)
-d = -19(6)
-d = -144
-d/-1 = -144/-1
d = 144
hope this helps