how to use chmod to change all permission in directory in linux code example

Example 1: debian give write permission

sudo chmod -R 757 /var/www

Example 2: linux chmod permissions

The three rightmost digits define permissions for the:
file user, the group, and others. 

#	Permission				rwx	Binary
7	read, write and execute	rwx	111
6	read and write			rw-	110
5	read and execute		r-x	101
4	read only				r--	100
3	write and execute		-wx	011
2	write only				-w-	010
1	execute only			--x	001
0	none					---	000