we know that
the formula to calculate the slope between two points is equal to
[tex]m=\frac{y2-y1}{x2-x1}[/tex]
in this problem
the rate of snowfall is equal to the slope of the linear equation
so
Let
x-------> the time in hours
y---------> the snowfall in inches
Step 1
Find the slope of the line of the Smithville city
Let
[tex]A(0,0)\\B(5,20)[/tex]
substitute the values in the formula above
[tex]m=\frac{20-0}{5-0}[/tex]
[tex]m=4\frac{inches}{hour}[/tex]
Step 2
Find the slope of the line of the Middletown city
Let
[tex]A(0,0)\\B(5,15)[/tex]
substitute the values in the formula above
[tex]m=\frac{15-0}{5-0}[/tex]
[tex]m=3\frac{inches}{hour}[/tex]
Step 3
Verify the statements
case A) Middletown had a faster rate of snowfall
The statement is False
Because Smithville had a faster rate of snowfall with [tex]4\frac{inches}{hour}[/tex]
case B) Smithville had a faster rate of snowfall
The statement is True
case C) Snow fell in Smithville at a rate of 4 inches per hour
The statement is True
case D) Middletown already had snow on the ground at the beginning of the storm
The statement is False
Because at the beginning of the storm the value of the snow is equal to zero
therefore
the answer is
Smithville had a faster rate of snowfall
Snow fell in Smithville at a rate of 4 inches per hour