a) (48 + k) • 8 = 400;

To solve the equation \((48 + k) \cdot 8 = 400\), follow these steps:

1. Divide both sides of the equation by 8 to isolate the term with \(k\):

   \[ 48 + k = \frac{400}{8} \]

   \[ 48 + k = 50 \]

2. Subtract 48 from both sides to solve for \(k\):

   \[ k = 50 - 48 \]

   \[ k = 2 \]

So, the value of \(k\) is \(2\).