Answer: 
k= -8 
Explaining:
Move variable to the left-hand side and change its sign. 
2.25k - 6.5k - 20= 6.5k - 6.5k + 14
Since two opposites add up to zero, remove them from the expression.
2.25k - 6.5k - 20= 14
Collect like terms! 
-4.25k = 14 + 20 
Add the numbers 
-4.25k = 35 
Divide both sides of the equation by -4.25
So you will get the answer: k= -8