Question

65% students passed & 420 students failed.
How many students attempted the test?

Answer 1

Let the total no of students be x,
65%  students passed,
Therefore, no of students passed =  $\frac{65}{100}$ × x = $\frac{13x}{20}$

No. of students failed = 420
The equation we can form,
x - $\frac{13x}{20}$ = 420

$\frac{20x - 13x}{20} = 420$

7x = 420 × 20

x = $\frac{420*20}{7}$

x = 1200

The total no of students who appeared the exam is 1200.

Answer 2

let the total no:of students be "X" 
no: of students passed = 65/100 * x = 13x/20
failed = 420
 X - 13x/20 = 420 
20x - 13x
---------------       = 420

7x = 420 * 20
x=420 * 20
_____________ _    =1200
       7
answer = 1200