Answer:
2.1
Explanation:
Simplifying 
3.4 + -2.8d + 2.8d + -1.3 = 0 
 
Reorder the terms: 
3.4 + -1.3 + -2.8d + 2.8d = 0 
 
Combine like terms: 3.4 + -1.3 = 2.1 
2.1 + -2.8d + 2.8d = 0 
 
Combine like terms: -2.8d + 2.8d = 0.0 
2.1 + 0.0 = 0 
2.1 = 0 
 
Solving 
2.1 = 0 
 
Couldn't find a variable to solve for. 
 
This equation is invalid, the left and right sides are not equal, therefore there is no solution.