Yeah I guess they mean one independent variable and one dependent variable
It rarely matters because if you had 2 dependent variables, you can just express that as 2 equations, so you might as well assume there's exactly 1 dependent and then only discuss the number of independent variables.
It rarely matters because if you had 2 dependent variables, you can just express that as 2 equations, so you might as well assume there's exactly 1 dependent and then only discuss the number of independent variables.