Answer:
The constant of proportionality is
![k=(6)/(5)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/h5x9dzg4l6890mv2y9wnjr1ttb4sjozqnm.png)
Explanation:
we know that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form
or
![y=kx](https://img.qammunity.org/2021/formulas/mathematics/middle-school/15ggalazf8cpjag5fv34y8ftpnv14l6oxo.png)
Let
x ----> the base of triangle
y ----> the height of triangle
To find out the constant of proportionality, divide the height by the base
First case
![x=7(1)/(2)=(7*2+1)/(2)=(15)/(2)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/iargt1matilfupo1614jn4uxeir901ibfi.png)
![y=9](https://img.qammunity.org/2021/formulas/mathematics/middle-school/hhut51em6vbs4zxwt1hw8nphad4ma0wnkp.png)
![k=(y)/(x)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/xtbkqw60469unlcz6l5dwj8wi12el8yb1c.png)
substitute
![k=9:(15)/(2)=(18)/(15)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/verg8v2zbxzgxmla7cmdbr5bqmd1rz3c1m.png)
Simplify
![k=(6)/(5)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/h5x9dzg4l6890mv2y9wnjr1ttb4sjozqnm.png)
Second case
![x=10(1)/(4)=(10*4+1)/(4)=(41)/(4)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/hlk2xzwpqkk4lapz5jiz3j9c4satqkoz47.png)
![y=12(3)/(10)=(12*10+3)/(10)=(123)/(10)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/8koh5c7vxd0wy0tqsivw8i97nmzcl0qlt3.png)
![k=(y)/(x)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/xtbkqw60469unlcz6l5dwj8wi12el8yb1c.png)
substitute
![k=(123)/(10):(41)/(4)=(492)/(410)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/g62klza42no35qcm5j7fm8qoas6vpv8cd1.png)
Simplify
![k=(6)/(5)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/h5x9dzg4l6890mv2y9wnjr1ttb4sjozqnm.png)
Third case
![x=16(3)/(4)=(16*4+3)/(4)=(67)/(4)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/h22d53rdy8iqfzxx7w7sbh6oihxv0lw7ib.png)
![y=20(1)/(10)=(20*10+1)/(10)=(201)/(10)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/rxcf19w4pihr967i8m1yse7jssrnlvd8xw.png)
![k=(y)/(x)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/xtbkqw60469unlcz6l5dwj8wi12el8yb1c.png)
substitute
![k=(201)/(10):(67)/(4)=(804)/(670)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/ylhhzm4c1jyyvdrnxm1pj6spyz7gn4vpjy.png)
Simplify
![k=(6)/(5)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/h5x9dzg4l6890mv2y9wnjr1ttb4sjozqnm.png)