Let's define Jennifer's share as $x$ dollars. Since Justin's share is $40 more than Jennifer's, Justin's share will be $x + 40$.

The total amount shared between them is $2,100, so we can set up the following equation:

$x + (x + 40) = 2,100$

Simplifying the equation:

$2x + 40 = 2,100$

Subtract 40 from both sides:

$2x = 2,060$

Now, divide by 2:

$x = 1,030$

a. Jennifer's share is $1,030.00.

b. To find Justin's share:

$x + 40 = 1,030 + 40 = 1,070$

Justin's share is $1,070.00.

Let me know if you'd like more details or have questions. Here are 5 related questions to expand on this:

1. How would the shares change if Justin's share was $60 more than Jennifer's?
2. What if the total amount shared was $3,000, with the same $40 difference?
3. What if Jennifer's share was $50 more than Justin's instead?
4. How would you set up the equation if the total was $2,100, but Justin got double Jennifer's share?
5. What if the total amount shared was split evenly between the two?

Tip: Always define variables clearly when solving word problems involving shared amounts to avoid confusion.