Answer:
-2.5
Explanation:
Simplifying 
20k + 50 = 0 
 
Reorder the terms: 
50 + 20k = 0 
 
Solving 
50 + 20k = 0 
 
Solving for variable 'k'. 
 
Move all terms containing k to the left, all other terms to the right. 
 
Add '-50' to each side of the equation. 
50 + -50 + 20k = 0 + -50 
 
Combine like terms: 50 + -50 = 0 
0 + 20k = 0 + -50 
20k = 0 + -50 
 
Combine like terms: 0 + -50 = -50 
20k = -50 
 
Divide each side by '20'. 
k = -2.5