Verified Answer :

Let's called this number x and sum it with 35

x+35

We know this sum is equal to 100, let's equal it.

x+35=100

\(\boxed { x+35=100 }\)

you can do any letter you want so let's say the sum of a number is n then u add 35 so it will be n+35 equals 100
n+35=100