Access denied from apt in Linux Mint

I’m actually using Linux Mint 18.04 on a 32-bit system, with an old computer, recently in dual-boot with Windows Vista. In the first times, I was able to download and install applications through terminal (with Konsole). But I come up with some problems. The first one is that I get "access denied" when I enter a command which needs apt file.

[sudo] password for ezer: 
sudo: unable to execute /usr/local/bin/apt: Permission denied
Hangup
ezer@admin-mintpower ~ $ su
Password: 
admin-mintpower ezer # sudo apt purge python2.x-minimal
sudo: unable to execute /usr/local/bin/apt: Permission denied
Hangup

I have tried to change owner but it doesn’t worked.
Any ideas ?