Question

if 5/9 of a piece of metal weight is 3kg then 2/7 of the piece of metal weight is how much?

Answer 1

if the mass is uniform in the metal then,
5x/9 = 3
=> x = 27/5
=> 2x/7 = 54/35 kg.

Answer 2

Let the weight of the metal be 'x'
A/Q
$\frac{5}{9} \times x = 3 \\ = > 5x = 27 \\ = > x = \frac{27}{5}kg$
So, $\frac{2}{7}$ would weight,
$( \frac{2}{7} \times \frac{27}{5} )kg = \frac{54}{35} kg$