Answer:
1 + 4x
Explanation:
Let's break this down.
"The sum of one" means that something is being added to the number one:
1 +
"and" whatever comes after the word 'and' will be added to the number one
"the product of 4 and a number x" this means that the number four and the variable x are being multiplied:
4x
Put it together:
1 + 4x
Therefore, the expression is 1 + 4x.