we have
x ------> the number of hours
y ------> the number of miles
we have that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form y=kx
where
k is the constant of proportionality or slope of the linear equation
In this problem the value of k=60 miles per hou
so
the linear equation is
y=60x
The slope is 60 miles/h (the slope is the same that the speed)
One point of the linear equation is (2,120)
that means-----> For x=2 hours, the distance is 120 miles