From the equations expressed as fractions, having a single variable,
gives;
[tex]1. \hspace{0.15 cm}\dfrac{4}{9} = \mathbf{\dfrac{10}{x}}[/tex]
By cross multiplying, to clear the fractions, in we have;
4 × x = 10 × 9 = 90
[tex]x = \dfrac{90}{4} = \mathbf{22.5}[/tex]
x = 22.5
[tex]2. \hspace{0.15 cm}\dfrac{5}{2} = \mathbf{\dfrac{6}{x}}[/tex]
5 × x = 6 × 2 = 12
[tex]x = \dfrac{12}{5} = \mathbf{2.4}[/tex]
x = 2.4
[tex]3. \hspace{0.15 cm}\dfrac{5}{2} = \mathbf{\dfrac{2}{x}}[/tex]
5 × x = 2 × 2 = 4
[tex]x = \dfrac{4}{5} = \mathbf{0.8}[/tex]
x = 0.8
[tex]4. \hspace{0.15 cm}\dfrac{21}{27} = \mathbf{ \dfrac{x}{18}}[/tex]
21 × 18 = 27 × x
[tex]x = \dfrac{21 \times 18}{27} = \mathbf{14}[/tex]
x = 14
[tex]5. \hspace{0.15 cm}\dfrac{15}{21} = \mathbf{ \dfrac{20}{y}}[/tex]
15 × y = 20 × 21
[tex]y = \dfrac{20 \times 21}{15} = \mathbf{28}[/tex]
y = 28
[tex]6. \hspace{0.15 cm} \mathbf{\dfrac{26}{b}} = \dfrac{39}{9}[/tex]
26 × 9 = 39 × b
[tex]b = \dfrac{26 \times 9}{39} = \mathbf{ 6}[/tex]
b = 6
Learn more about cross multiplications method here:
https://brainly.com/question/19708346