Question 1118395
<br>
The solution (or partial solution) by the other tutor is fine; and finding the solution using formal algebra can be a good exercise in the use of algebra.  But if an algebraic solution is not required, the answer can be found with much less work.<br>
9 out of 20 students take a bus.  One-third as many come by van; that is 3 out of 20.<br>
The remaining 8 out of 20 come by car; that is 720 students.<br>
Using mental arithmetic 8 out of 20 being 720 means 1 out of 20 is 90; the number of students in the school is then 20*90 = 1800.