The greatest whole possible whole number length of the unknown side is 9 inches
<em><u>Solution:</u></em>
Two sides of an acute triangle measure 5 inches and 8 inches
The length of the longest side is unknown
We have to find the length of unknown side
The longest side of any triangle is a hypotenuse
<em><u>For a acute triangle we know:</u></em>
If c is the longest side of a acute triangle, a and b are other two sides of a acute triangle then the condition that relates these three sides are given as:

Here in this sum,
a = 5 inches
b = 8 inches
c = ?
Substituting we get,

On rounding to nearest whole number,
c < 9
Hence, to the greatest whole possible whole number length of the unknown side is 9 inches