Answer:
k = 80
Explanation:

We can convert the decimal from - 0.8 into - 8/10.

Rewrite the equation.

Move 10 to multiply - 64

Then we move - 8 to divide - 640.

Dividing both negative equal positive. Therefore, the value of k is 80.
Answer Check
Substitute k = 80 in the equation.

The equation is true. Therefore, 80 is the right answer.