(length)*(width) = Area = 80
(length) = 1.25*(width)
replace what the length equals for the length
in the first equation to get:
1.25*(width)*(width) = 80
(width)^2 = 64 [divided 1.25 from both sides]
(width) = 8 [square rooted both sides]
plug this (width) back into the second equation
(length) = 1.25*(8) = 10
so (width) = 8
and (length) = 10