ANother Problem with KERNELS

[AJavi]

On my Linux Mint guest


sudo apt-get install linux-headers-$(uname-r)
uname-r: command not found
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package linux-headers is not installed, so not removed
0 upgraded, 0 newly installed, 0 to remove and 404 not upgraded.

this is getting very frustrating because everytime i get closer to solving this Guest Additons nonsense something else doesnt work. i need to run guest additions properly so i can get the auto resize option to make my screen bigger. please help me
-thanks

[Perryg]

uname -r

notice the space