5/4 is the constant of proportionality
I believe that the answer is 14 or 7
Answer:

And replacing we got:

And then the estimator for the standard error is given by:

Step-by-step explanation:
For this case we have the following dataset given:
20.05, 20.56, 20.72, and 20.43
We can assume that the distribution for the sample mean is given by:

And the standard error for this case would be:

And we can estimate the deviation with the sample deviation:

And replacing we got:

And then the estimator for the standard error is given by:

Answer:
josh vendió 17 libros recaudando 306 dolares .
jessica vendió 255 libros recaudando 4590 dolares.
Step-by-step explanation:
Sustituimos por variables :
libros que vendió Jessica = x
libros que vendió Josh = y
entonces:
x + y = 272
Jessica vendió 15 veces mas libros que josh:
x = 15y
Reemplazamos en la anteriior ecuacion:
15y +y = 272
16y = 272
y = 17
Reemplazamos en la primela ecuacion :
x + 17 = 272
x = 255