If a and b are positive integers,
Question:

If a and b are positive integers, then the solution of the equation ax = b has to be always

(a) positive

(b) negative

(c) one

(d) zero

Solution:

(a) If $a x=b$, then $x=\frac{b}{a}$

Since, a and b are positive integers. So, $\frac{b}{a}$ is also positive integer, Hence, the solution of the given equation has to be always positive.