Algebra practice

1:
Fatal error: Uncaught Error: Call to undefined function get_o2() in /var/www/vhosts/ent.storkey.uk/html/inc/dynaPage.php:3542 Stack trace: #0 /var/www/vhosts/ent.storkey.uk/html/inc/reporting2.php(360): questionm->__construct('algexpsimpq1', Array) #1 /var/www/vhosts/ent.storkey.uk/html/inc/dynaPage.php(189): echo_value('algexpandxaa', 'content', Array) #2 /var/www/vhosts/ent.storkey.uk/html/inc/dynaPage.php(742): dynaPage->echo_value('content') #3 /var/www/vhosts/ent.storkey.uk/html/inc/dynaPage.php(179): mainPanel->write('main-panel') #4 /var/www/vhosts/ent.storkey.uk/html/index.php(21): dynaPage->write() #5 {main} thrown in /var/www/vhosts/ent.storkey.uk/html/inc/dynaPage.php on line 3542