Step 1: Write the given data.
Initial position:
\[
x_0=3\;\text{cm}
\]
Initial velocity:
\[
u=12\;\text{cm s}^{-1}
\]
Final position after \(t=2\;\text{s}\):
\[
x=-5\;\text{cm}
\]
Acceleration \(a\) is to be found.
Step 2: Use the equation of motion.
For uniform acceleration,
\[
x=x_0+ut+\frac12 at^2
\]
Substituting the given values,
\[
-5=3+(12)(2)+\frac12 a(2)^2
\]
\[
-5=3+24+2a
\]
\[
-5=27+2a
\]
Step 3: Solve for acceleration.
\[
2a=-5-27
\]
\[
2a=-32
\]
\[
a=-16\;\text{cm s}^{-2}
\]
Hence,
\[
\vec{a}=(-16\;\text{cm s}^{-2})\hat{i}
\]
Step 4: Final conclusion.
Therefore, the acceleration of the object is
\[
\boxed{\vec{a}=(-16\;\text{cm s}^{-2})\hat{i}}
\]