If x varies directly with y, then :
● Increase in x results in increase of y
● Decrease in x results in decrease of y
● It is represented by : x ∝ y
[tex]\mathsf{\bigstar\;\;If\;x\;varies\;directly\;with\;y\;then : \large\boxed{\mathsf{\dfrac{x_1}{x_2} = \dfrac{y_1}{y_2}}}}[/tex]
Here : x₁ = 6 and y₁ = 15 and x₂ = x₂ and y₂ = 20
Substituting the values we get :
[tex]\mathsf{\implies \dfrac{6}{x_2} = \dfrac{15}{20}}[/tex]
[tex]\mathsf{\implies x_2 = \dfrac{20 \times 6}{15}}[/tex]
[tex]\mathsf{\implies x_2 = 8}[/tex]
Answer : x = 8 when y = 20
