Answer :
For this case we have that by definition, a direct variation is given in the form:
[tex]y = kx[/tex]
Where:
k: It is the constant of proportionality
According to the statement we have to:
[tex]y = 25\\x = 4[/tex]
Substituting:
[tex]25 = k4\\k = \frac {25} {4}[/tex][tex]k = 6.25\ for\ \frac {dollars} {hour}[/tex]
On the other hand we have:
[tex]y = 4\\x = 25\\4 = k25\\k = \frac {4} {25}[/tex]
[tex]k = 0.16\ for\ \frac {hours} {dollar}[/tex]
Answer:
[tex]k = 6.25 for \frac {dollars} {hour}\\k = 0.16 for \frac {hours} {dollar}[/tex]