Answer:
The answer is D.
Step-by-step explanation:
The phrase "20 decreased by the sum of 6 and b." means that since the word sum is the word for the result of two numbers being added together, it would make sense if you look at ( 6 + b ), and since you're also decreasing the result by 20, that would mean subtracting it by 20, so you get 20 - ( 6 + b ).
I hope this helps you :D
