Incorrect Hint and Solution
For Kirchhoff's circuit laws, we need to take into account both the circuits and the voltages (encoded as linear equations). For the voltage portion of Kirchoff's laws, resistors are also included as voltage = current x resistance.
MATH152/April 2016/Question A 25
Actually, you are correct (and the hint looks good). However, it may be helpful for students if you made your solution more clear (for instance, applying Kirchoff's circuit laws to which node of the diagram).
This one is based on the notes http://www.math.ubc.ca/~elyse/152/2018/5Circuits.pdf
Again, I am not an expert on such questions though I tried to spend some time going through the lecture notes online and learn it, so please feel free to add more details to the solutions.
For this question, I think it only asks one linear equation that matches the loop currents to the current source, so I am not sure whether we should consider the resistor * current= voltage equation.