Answer:
Suppose that Yumiko has the linear system
[tex]2x-3y=12 \;;(1)\\ax+by=c \;; (2)[/tex]
Since she multiplies the first equation by 6 then she obtains the equation
[tex]12x-18y=72[/tex]
Then, if she want to eliminate the variable y, she should multiply the equation (2) by [tex]\frac{-12}{a}[/tex] because when performing the multiplication, the coefficient that accompanies the x become 12.
If she want to eliminate the variable y, she should multiply the equation (2) by [tex]\frac{3}{b}[/tex] because when performing the multiplication, the coefficient that accompanies the y become 3.