Of the 1,640 students enrolled at a school, 50% come to school by bus, 35% come by car, and the rest of the students walk home. how many students walk to school?

So first we need to find what percent of the students walk to school. 

50 + 35 = 85% don't walk leaving only 15% that walk to school, 

To find the 15% percent that DO walk we multiply .15 by the total number of people. 

.15 x 1640 = 246 people walk to school 

1,640 / 2 = 820
35 of 1640 is 574
820 + 574 = 1,394
1,640 - 1,394 = 246

Hope this helps