Let's start by setting up an equation based on the given information.
Let Ivan's current age be x. Then his age next year will be x + 1.
We know that the sum of Ivan's current age and his age next year is 79:
x + (x + 1) = 79
Simplifying the equation, we get:
2x + 1 = 79
Subtracting 1 from both sides, we get:
2x = 78
Dividing both sides by 2, we get:
x = 39
So Ivan's current age is 39.
To find out how old Ivan will be 18 years from today, we can simply add 18 to his current age:
39 + 18 = 57
Therefore, Ivan will be 57 years old 18 years from today.