After you substitute $t=3$, handle the exponent on 3 first (the $t^2$ part), then multiply by 2, and only then do the subtraction from 9.

Make sure you keep the 9 at the beginning of the expression and subtract the whole product $2\cdot(3^2)$ from it, rather than adding or dropping any part.

In the Desmos expression line, type 9 - 2(3)^2. Desmos will show a single numeric output; that number is the value of $h(3)$ according to the function $h(t)=9-2t^2$.

The function is defined by $h(t)=9-2t^2$.

The notation $h(3)$ means: plug in $t=3$ everywhere you see $t$ in the formula.

So start by writing:

Use the order of operations: exponents first, then multiplication, then subtraction.

1. Compute the exponent: $3^2=9$.
2. Multiply by 2: $2\cdot 9=18$.

So the expression becomes:

Now simplify the subtraction:

So the value of $h(3)$ is $-9$.