Answer:
[tex]59.6[/tex] mm
Step-by-step explanation:
We know that the base times the height divided by two is the area, so we have that [tex](8.6*h)/2=256.28[/tex].
We can multiply both sides by [tex]2[/tex] to get [tex]8.6*h=512.56[/tex].
Lastly, we divide by [tex]8.6[/tex] on both sides to get [tex]h=512.56/8.6[/tex].
This simplifies to [tex]\boxed{h=59.6}[/tex] mm!