Question 662248
I imagine that by "an open cube" the problem means an open cube-shaped box, with 5 faces, but missing the lid.
If that net shows 5 squares, for 5 congruent faces of a cube,each having the same area, the surface area of each face is
{{{45cm^2/5=9cm^2}}}
The area of a face in a cube with side {{{x}}} cm is {{{x^2}}} {{{cm^2}}}, so in this case
{{{x^2=9}}} --> {{{x=sqrt(9)}}} --> {{{highlight(x=3)}}}
The side of the cube measures {{{highlight(3cm)}}}.