Simple...
remember A(B+C)=AB+AC
You have to have a common factor in both terms..(number)..this number would be 6.
So we know it has to have 6 in your answer.
If we plug n chug..:
206+205=220
640+65=270
640+6=246
64+65=54
645= 270
This being said, 640+65 is the choice you need.
Thus, your answer.
