what are 3 types of systems in two variables?

Question

var fctb_tool=null; function PW__hu_im6aE(t) { fctb_tool=t; start(fctb_tool); } what are 3 types of systems in two variables?  What type of answer will you get for each of the 3 types of systems?

Answer 1

var fctb_tool=null; function W_CV_cM0QzB_(t) { fctb_tool=t; start(fctb_tool); }

Answer 2

igneous,sedimentary and metamorphic rocks