Answer:
Pat a) The unit rate of graph at left is 
Part b) The unit rate of graph at right is 
see the attached figure
Step-by-step explanation:
we know that
The unit rate of a linear equation is the same that the slope of the linear equation
step 1
Find the slope of the graph at left
This graph represent a proportional relationship (because the line passes through the origin)
The slope is equal to the constant of proportionality k

we have the point (1,25)
substitute the values in the formula

step 2
Find the slope of the graph at right
we have the points (2,80) and (3,120)
This graph represent a proportional relationship (because the line passes through the origin)
The slope is equal to the constant of proportionality k

Is necessary only one point to determine the constant of proportionality
take the point (2,80)
substitute the values

<u>Verify</u>
The formula to calculate the slope between two points is equal to

we have the points (2,80) and (3,120)
substitute the values

