The person is walking 3.5 miles an hour

Actually Welcome to the Concept of the Force.
Force = Mass * Acceleration.
here, Mass = 45 kg and Force = 65 N
hence, Acceleration = 65/45
===> Acc. = 1.44 m/s^2
hence the acceleration is 1.44 m/s^2
Take into account that density and relative density are given by:

Take into account that the volume associated to each of the given sustances in the table is determined by the Level Difference (because it is the change in the volume of the water of the recipient in which the substance is immersed).
The density of water in kg/m^3 is 1000 kg/m^3.
Due to the density must be given in kg/m^3, it is necessary to express the volumes of the table in m^3 and mass in kg, then, consider the following conversion factor:
1 m^3 = 1000000 ml
1 kg = 1000 g
Then, you obtain the following results:
Brass:

Cooper:
I think It would be C. Checking a prediction. Sorry if I’m wrong
Answer:
The image distance is 20.0 cm.
Explanation:
Given that,
Power = 1.55 dp
Distance between book to eye = 26.0+3.00=29.0 cm
We need to calculate the focal length
Using formula of focal length

Put the value into the formula



We need to calculate the image distance
Using lens formula


Put the value into the formula



Hence, The image distance is 20.0 cm.