I was reading Hayt Kemmerly Engineering Circuit Analysis Book,(I tried others, but this is the most comprehensible to me.), And I came across this circuit. I understand the first two, but I don't understand how, in the 3rd circuit (c), there is negative voltage through the resistor \$R_3\$ , while the current through it from \$+\$ to \$-\$ is positive \$7A\$. I don't understand how resistors can supply voltage. My guess is this is only a mathematical model, not real.
Edit: The Answers are shuffled in this book. Edit 2: It looks like this book is not in the public domain, as I originally thought. However, I am not removing this image because it falls under fair use.