Proportions
Two magnitudes are proportional if one of them can be calculated as the other by a constant number. That is:
y=k.x
Where y is one magnitude or variable and x is the other. K is the constant of proportionality
The information given in the question states the Daniel earns $37 for 4 hours.
Let's call E to his earnings, and h to the hours he works, thus:
E=k.h
We don't know yet the value of k.
Let's use the previous data to find k E=37 when h=4:
37 = k*4
Find k by solving the above equation. Dividing by 4:
37 / 4 = k
Thus:
k = 9.25
Knowing the value of k, the function is:
E = 9.25*h
Please note that for h=7:
E = 9.25*7= $64.75
The second data corresponds to the already-found value of k, thus:
The constant of proportionality is 9.25