Answer:
The we equation is
![y = (2)/(5)x](https://img.qammunity.org/2021/formulas/mathematics/middle-school/ushdpqlnbhu6rocc0zltxfw0q6cq4wubyj.png)
The constant of proportionality is
![k = (2)/(5)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/dky3ei4th8oaxm9aiulsotf35qzoe8o7fq.png)
Explanation:
The given point is
![(5 (5)/(8) ,2 (1)/(4) )](https://img.qammunity.org/2021/formulas/mathematics/middle-school/x4bv7dxl9qs2cweabnft6vt2div1hp0x0v.png)
A proportional relationship has a general equation of the form:
![y = kx](https://img.qammunity.org/2021/formulas/mathematics/middle-school/1gd3aqw83dm1pbbole5g3vytvoi3pw440d.png)
We substitute the point into the equation to get:
![2 (1)/(4) = 5 (5)/(8)k](https://img.qammunity.org/2021/formulas/mathematics/middle-school/r9a06xc0xo1s82j8s17pi7f6rwm55yi8pg.png)
Change to improper fractions to get:
![(9)/(4) = (45)/(8)k](https://img.qammunity.org/2021/formulas/mathematics/middle-school/c1g8jeur397ih0w170r7x0zt3rha92rngz.png)
We multiply through by
![(8)/(45)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/cg3drysxxgk5gcmdgg7vn5aoyhqcv3afc6.png)
This gives us:
![(8)/(45) * (9)/(4) = k](https://img.qammunity.org/2021/formulas/mathematics/middle-school/lpst5uosuro7q6dubq21lfpi036b8qytay.png)
![k = (2)/(5)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/dky3ei4th8oaxm9aiulsotf35qzoe8o7fq.png)
The equation is
![y = (2)/(5)x](https://img.qammunity.org/2021/formulas/mathematics/middle-school/ushdpqlnbhu6rocc0zltxfw0q6cq4wubyj.png)