Where value(t)=$1000(1.07)^t. When the value is (t+3) how do you find the answer for the unknown when you put the unknown back into the equation? Or is (t+3) in the equation the answer?
value(t+3)=$1000(1.07)^(t+3).
This could be simplified using order of operations and laws of exponents, but the for this question the answer is correct as shown above.
For future reference:
Recall that a^(b + c) = a^b * a^c. So
$1000 ( 1.07)^(t + 3) =
$1000 ( 1.07)^t * (1.07)^3.
We can calculate 1.07^3. We get something like 1.23. Your calculator will tell you whether my mental calculation was right, but if it was we then see that
$1000 ( 1.07)^t * (1.07)^3 =
$1000 ( 1.07)^t * 1.23 =
$1230 (1.07 ^ t),
approximately.