Question

7x - 21y = 20, then how many positive integer solutions does the equation have?​

Answer 1

7x - 21y = 20 is a Linear equation in two variables .

So , it has infinitely many solutions.

But this equation doesn't have any positive integer solutions.

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Answer 2

Given:

7x-21y=20

To find:

positive solutions = ?

Solution:

value:

$\Rightarrow 7x-21y=20$

In the given equation if we put x = 1 so, it will give:

$\Rightarrow 7(1)-21y=20\\\\\Rightarrow 7-21y=20\\\\\Rightarrow 21y=20-7\\\\\Rightarrow 21y=13\\\\\Rightarrow y= \frac{13}{21}$  

And when we put y=1. So, it will give:

$\Rightarrow 7x-21(1)=20\\\\\Rightarrow 7x-21=20\\\\\Rightarrow 7x=20+21\\\\\Rightarrow 7x=41\\\\\Rightarrow x= \frac{41}{7}$

In which both the given value is not positive, and for more please find the attachment.