Question

For the equation x/3=15 a student found the value of x to be 5.explain the error

Answer 1

Let plug the variable into the equation.

$x = 5$
$5/3=15$

We can conclude that this is incorrect because $5/3$ does NOT equal $15$

The correct answer would be: $15/3 = 5$; $15/5=3$; or
 $3(5) = 15$ or $45/3=15$

All $4$ of these are correct answers. 

Answer 2

Input the answer the student obtained:
x/3=15
x=5
5/3=15
5/3
=1.6667
1.6667≠15

The Correct Answer:
Solve for x.
x/3=15
Multiply both sides by 3.
(x/3)*3=(15)*3
x=45

To check, input the answer in the equation:
45/3=15
15=15

The answer would be 15.

Hope this helps.
-Benjamin