Step-by-step explanation:
If 2 triangles are similar then the ratio of any 2 sides of one triangles will be equal to the ratio of any 2 sides of the another triangle.
So,
[tex] \frac{30}{8} = \frac{20}{y} [/tex]
Cross-multiplying the denominators gives,
[tex]30y = 160[/tex]
[tex] = > y = \frac{160}{30} = \frac{16}{3} [/tex]
