The fromula of a surface area of a rectangular prism:
[tex]SA=2lw+2lh+2wh[/tex]
w - width
l - length
h - height
We have
[tex]SA=488\ cm^2,\ l=14\ cm,\ w=6\ cm[/tex]
Susbtitute:
[tex]2(14)(6)+2(14)(h)+2(6)(h)=488[/tex]
[tex]168+28h+12h=488[/tex] subtract 168 from both sides
[tex]40h=320[/tex] divide both sides by 40
[tex]\boxed{h=8\ cm}[/tex]