Answer:
D. 
Step-by-step explanation:
We have been give an equation
. The equation is solved by combining like terms. We are asked to choose the equation that an be solved by combining the like terms.
Let us check our given choices one by one.
A. 
We can see that equation A will be solved by dividing 20 by 5, therefore, option A is not correct choice.
B. 
We can see that equation B will be solved by dividing 20 by 5 and then subtracting 5, therefore, option B is not correct choice.
C. 
We can see that equation C will be solved by multiplying 20 by 4, therefore, option C is not correct choice.
D. 
We can see that equation D will be solved by combining like terms, therefore, option D is correct choice.