Let's consider that number to be 'x'..
So, twice the number (2x) is 12 greater than than the half of the number.
So the equation will be like,
2x=12+x/2
Solving this further,
2x=(24+x)/2
=> 4x=24+x
=>4x-x=24
=>3x=24
=>x=8..
So the number is "8".
5 x 10^-6
=0.000005 <span> in standard notation</span>
hope that helps
Last one is your answer
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Part a: 6:3 > 2:1
part b: 9:3> 3:1
D.
or divide 900 by 20 and see the closest