#{:
(color(blue)(2x+5y=16),"after multiplication by " 5 " gives",color(white)("x")color(blue)(10x+25y=80)),
(color(blue)(-5x-2y=2),"after multiplication by "2" gives",ul(color(blue)(-10x-4y=color(white)("x")4))),
(,"adding the revised forms of the two equations:",color(blue)(21y=84)),
(,rarr color(blue)(y=84/21=4),)
:}#

Similarly

#{:
(color(blue)(2x+5y=16),"after multiplication by " 2 " gives",color(white)("x")color(blue)(4x+10y=32)),
(color(blue)(-5x-2y=2),"after multiplication by "5" gives",ul(color(blue)(-25x-10y=color(white)("x")4=10))),
(,"adding the revised forms of the two equations:",color(blue)(-21x=36)),
(,rarr color(blue)(x=-42/21=-2),)
:}#