D
Explanation
Step 1
Let
x represents the smallest number:
[tex]x[/tex]as those are three consectutive intergers, the next interger is:
[tex]x+1[/tex]this is the middle number:
middle number=x+1
the next consectutive number is
[tex]\begin{gathered} x+1+1 \\ x+2 \end{gathered}[/tex]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)
[tex]\begin{gathered} (x)+2(x+1)=20+(x+2) \\ (x)+2(x+1)=(x+2)+20 \end{gathered}[/tex]so, the answer is
D