Question

solve each equation system by the addition method 3x+5y=21 -9x+4y=-6

Answer 1

to use the addition/elimination method
choose one of the variables and use the appropriate factors to make the coefficients equal and opposite so that when you add the equations the variable is eliminated.
you have one linear equation with one unknown. solve.
use this value in either of the originals to get the value of the other variable.

Answer 2

for this I would multiply the first equation by 3

Answer 3

do you get y = 3?