Answer
$D)$ $6+2x=72$
Work Step by Step
Let's translate English terms into mathematics terms.
"Is" in English means "equal" in math, which results in $=72$ on one side of the equation.
"Twice the number" - lets say the number we are talking about is $x$ - means it is $2$ times the number $x$; resulting in $2x$.
"Six more" means that we would add six in the equation on the side of the term $2x$.
We get the equation
$72 = 2x +6$.
We can also rearrange the equation in way that results in
$6 + 2x = 72$.
In order to solve the equation, we move the like terms on one side and the unlike terms on the other. In this question, we move $6$ to the other hand which makes it $72-6$ which is $66$ and on the left hand we have $2x$. We then take the two which is multiplied by $x$ since it is a like term and move it to the right-hand side to get $66/2$ which is $33$.
Note: When we move terms to the other side, they change symbols
a (-) sign turns into a (+) sign and a ($\times$) sign changes to a ($\div$) and vice versa.