Question

30% of Number A is the same as 40% of Number B.

Answer 1

30% of number A means

$\dfrac{30A}{100}=\dfrac{3A}{10}$

similarly, 40% of number B means

$\dfrac{40B}{100}=\dfrac{2B}{5}$

These must be equal, so we have

$\dfrac{3A}{10}=\dfrac{2B}{5}$

Multiply both sides by 10 to get

$3A=4B \iff A=\dfrac{4B}{3}$

So, you can choose any number for A, and then you multiply it by 4/3 to get B. There are infinitely many solutions to this equation.