Answer:

Step-by-step explanation:
We want to find

This can be rewritten as;


Recall that; 

We evaluate now to obtain;

Answer:
see explanation
Step-by-step explanation:
If y is proportional to x then the equation relating them is
y = kx ← k is the constant of proportion
To find k divide both sides by x
k = 
This value must be constant for all ordered pairs, thus
k =
= 
k =
= 
k =
= 
k = 
Since k is constant for all ordered pairs then y is proportional to x
Y = kx
Plug in what we know:
5 = k(8)
5 = 8k
Divide 8 to both sides:
k = 0.625
Plug this back into the equation along with y = 15:
y = kx
15 = 0.625x
Divide 0.625 to both sides:
x = 24