Answer: B
Step-by-step explanation:
To solve for the blank, let's put an x there for placement. All that's needs to be done is to combine like terms and solve.
[tex](x*5)*(1*2)=20[/tex] [multiply]
[tex]10x=20[/tex] [divide 10 on both sides]
[tex]x=2[/tex]
Therefore, the answer choice that matches is B.