You can also use numbers to represent the permissions.
4 is for Read, 2 is for Write and 1 is for Execute permission.
The following diagram shows if the user has all three permissions rwx and group has only read and execute permission and others have only read permissions, the rwxr-xr-- can be represented by 754.
So, for a file with permissions rwxr-xr-x, the owner has rwx permission which 4+2+1=7 and group and others have r-x which means 4+0+1 = 5. Thus the command you would use to set such permission would be: chmod 755 myfile.
Taking you to the next exercise in seconds...