Question 546125
the number of people seated is 
{{{ 900 - 9 = 891 }}}
Let {{{ s }}} = number of students at Lincoln High
Let {{{ t }}} = number of teachers at Lincoln High
given:
(1) {{{ s = 26t }}}
(2) {{{ s + t = 891 }}}
Substitute (1) into (2)
(2) {{{ 26t + t = 891 }}}
(2) {{{ 27t = 891 }}}
(2) {{{ t = 33 }}}
and, since
(1) {{{ s = 26t }}}
(1) {{{ s = 26*33 }}}
(1) {{{ s = 858 }}}
There are 858 students at Lincoln High