697 (option C)
Step-by-step explanation:
From 100 students:
Number of students tha t work to school = 82
Number that don't walk to school = 18
If there are 850 students:
let the number of those who work to school = y
82 who walk = 100 total
y who walk = 850 total
cross multiply:
82(850) = y(100)
69700 = 100y
100y/100 = 69700 /100
y = 697
The principal should expect 697 students will walk to school (option C)