How do you translate into a mathematical expression: Twice the sum of eight more than a number?
The word "SUM" means ADD and should always be used with the word "AND" to indicate which numbers are being added,.
In this case, I suspect the expression could be written as.
"Twice the sum of 8 and a number"
The sum of 8 and a number is written as
"Twice" means "double" or multiply by 2.