I have problems

Hi guys, I just added a new user to my website. After i did it, every time i try to post something on it. It shows me this following message:
“Fatal error: Allowed memory size of 100663296 bytes exhausted (tried to allocate 25243247 bytes) in /home/content/68/7982668/html/wp-includes/wp-db.php on line 885”

I really need help on this.