Kelsey has a marbles, Gena has b marbles, and Noah has c marbles. If Kelsey has more marbles than Gena and Noah combined, write an expression (using a, b, and c) that shows how many more marbles Kelsey has than Gena and Noah combined.

a = ? + b+c

I suspect you left out how many more Kelsey has...

Let's start by adding the number of marbles Gena and Noah have together.

Gena + Noah = b + c

Now, we need to subtract the sum from the number of marbles Kelsey has to find how many more marbles she has than Gena and Noah combined.

Kelsey - (Gena + Noah) = Kelsey - (b + c)

Therefore, the expression that shows how many more marbles Kelsey has than Gena and Noah combined is:

Kelsey - (Gena + Noah) = Kelsey - (b + c)

To find the expression that represents how many more marbles Kelsey has than Gena and Noah combined, we need to calculate the sum of marbles owned by Gena and Noah and then subtract this sum from the number of marbles owned by Kelsey.

The sum of marbles owned by Gena and Noah is given by b + c.

Therefore, the expression that represents how many more marbles Kelsey has than Gena and Noah combined is:
a - (b + c)