How to code like this thing?

Projects Programming
1

Hello everyone
I want to excute when some variable is between 11 to 80
but its too long to write

if(var == 11 || 12 || 13|| .......)

this is not a good code!
but I dont know good way to write this
please help me

2 
if (var > 10 && var < 81)
3

The hard way to do it is:

if((var == 11)||(var == 12)||(var == 13)||...)

The easy way is:

if((var >= 11) && (var <=80))
4 
if(val>=11 && val <=80)
{
 ...
  
..
}
5

ah.... why I couldnt remember those method...!
thanks everyone!