So i need on how to find the missing angle, can someone me on how to solve it?

Triangle xyz has vertices x(1,3), y(0,0)

Which of the following is the explicit rule for a geometric sequence defined a recursive formula of a -5a for which the first term is 23?

Aclassmate thinks that solving a system by graphing gives an exact answer when the lines appear to cross at a grid point, but only an approximate answer when they don't. explain why this isn't true.