Question

Q. The cost of a pen is four times the cost of a pencil. Write a linear equation in two variables to represent this situation.
A. solution1
4x - y + 0=0
solution 2
4x-y = 0

I wanted to know which solution is correct and why?

Answer 1

Both of the solution are correct. You just added an extra zero in the Solution zero.

Solution:
let us take that cost of a pencil is x and cost of the a pen is y

Then we can write:
y = 4*x

On taking 4x in LHS y - 4x = 0 (SOLUTION 1, CORRECT)

we can add zero to the both side of solution 1, it will be same.

y - 4x +0 = 0 + 0

y - 4x + 0 = 0 (SOLUTION 2, CORRECT AND SAME AS SOLUTION 1)