Let's start with the expression:

Five time the sum of a number and 4.

Let's let "a number" be X.

Five time the sum of X and 4

When it says "Five times the sum", we know that the next two variables will be added together.

Five time (the sum of X and 4)

When you see " the sum of" some number and another number, this means both numbers will be added together.

Five times (X + 4)

"times" means multiplication so the end expression is

5 x (X + 4)

In math, when you have a number next to parenthesis, multiplication is implied.

5(X+4)