a) $121-12 x=-x-4$
\(\boxed{x = \frac{125}{11}}\)
Step 1 :\(121 - 12x = -x - 4\)
Step 2 :\(121 - 12x + x = -4\)
Step 3 :\(121 - 11x = -4\)
Step 4 :\(-11x = -125\)
Step 5 :\(x = \frac{125}{11}\)
Step 6 :\(\boxed{x = \frac{125}{11}}\)