From Mechanics

Here \displaystyle T is the tension in the cable and \displaystyle a is the acceleration of the packet.

The acceleration is in the opposite direction to the motion.This means mathematically the acceleration is negative, \displaystyle a=-0 \textrm{.}1\text{ m}{{\text{s}}^{\text{-2}}}

Applying Newton's second law

\displaystyle \begin{align} & \uparrow :\ \text{Resultant}\ \text{Force}=T-300\times 9 \textrm{.}81= ma = 300\times (-0 \textrm{.}1) \\ & \\ & T=-30+2943\approx 2910\ \text{N} \\ \end{align}