Mod is something like the remainder of the expression, but it’s more complicated than that.

I believe you know what ln is.

The left side is a ceiling function. just round up to the nearest whole number.

The right side is 30 modulo 5, you can treat it here as the remainder when 30 is divided by 5

I never saw the ceiling function and thought it was regular brackets.

Actually im totally unsure of how to solve this qns ( this is from poly not JC but there was no poly option)

The one which looks kind [ ] but without the two bottom lines of the brackets is called the ceiling function. Whenever we apply the ceiling function to a number, we round up that number to the nearest whole number. So the ceiling of 5.99 is 6, while the ceiling of 5.01 is also 6.

The contrasting term is the floor function which rounds numbers down. This is represented by [ ] without the top two lines.

As for mod, it’s something like remainder. “1707 mod 2” is like asking “find the remainder when 1707 is divided by 2”.