To determine the height of the baseball after 3.5 seconds, we use the given expression for height:
[tex]\[
-16t^2 + 64t + 3
\][/tex]
Here, [tex]\( t \)[/tex] represents the time in seconds. We are asked to find the height when [tex]\( t = 3.5 \)[/tex].
Substitute [tex]\( t = 3.5 \)[/tex] into the expression:
[tex]\[
-16(3.5)^2 + 64(3.5) + 3
\][/tex]
Calculating the above expression gives:
[tex]\[
\text{Height} = 31 \text{ feet}
\][/tex]
Therefore, the height of the baseball after 3.5 seconds is [tex]\( 31 \)[/tex] feet.
So, the answer is:
[tex]\[
\boxed{31}
\][/tex]
