Help. php-mbstring : Depends: php7.0-mbstring, Unable to correct problems, you have held broken packages Ubuntu 16.04
sudo apt-get install phpmyadmin php-mbstring php-gettext Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: php-mbstring : Depends: php7.0-mbstring but it is not going to be installed E: Unable to correct problems, you have held broken packages.
It appears that you needed to install them in a sequence so any dependencies will be taken care, so the way aught to have been:
sudo apt install php7.0-common php7.0-mbstring php-mbstring