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:

it would be:

c.parallelogram.

example 2 – simplify: step 1: completely factor both the numerators and denominators of all fractions. step 2: change the division sign to a multiplication sign and flip (or reciprocate) the fraction after the division sign; essential you need to multiply by the reciprocal. step 3 : cancel or reduce the fractions.