Let
x = volume in liters of 4% solution
y = volume in liters of 10% solution
$x + y = 5$
$y = 5 - x$ ← Equation (1)
$4x + 10y = 6(5)$
$4x + 10(5 - x) = 30$
$4x + 50 - 10x = 30$
$6x = 20$
$x = 3.33 ~ \text{liters}$
From Equation (1)
$y = 5 - 3.33$
$y = 1.67 ~ \text{liters}$
Thus, [ A ] answer