19. why are the substitution and elimination methods necessary when we already know how to solve systems of linear equations using the graphing method?

There are situations in which you may be required to solve a system of equations and no graph is present or available. In these instances, substitution and elimination are very effective solution methods.

Step-by-step explanation:

i dont know

step-by-step explanation:

let m = monomial

let t = trinomial

so, m times t = t.

monomial times a trinomial = another trinomial.