D
Step-by-step explanation
Step 1
Let
x represents the smallest number:

as those are three consectutive intergers, the next interger is:

this is the middle number:
middle number=x+1
the next consectutive number is

so, the third number is x+2
Hence,
Step 2
the sum of the smallest number and twice the middle
number is equal to 20 more than the third number?
replacing:
twice the middle=2(x+1)

so, the answer is
D