2 * (w - 5) = 6
What you do is read the sentence and make an equation. So let's do that.
"Twice the difference of a number and 5 is equal to 6"
There's several parts. "Twice the difference" indicates that you're multiplying by 2, and "difference of a number and 5" would indicate subtraction. And finally, "is equal to 6" would indicate an equality. So let's make the equation.
"Twice the difference"
2 * ?
"difference of a number and 5"
2 * (w - 5)
""is equal to 6"
2 * (w - 5) = 6
So your desired equation is
2 * (w - 5) = 6