Let's denote the cost of the 2-inch marble as \( x \) cents. Accordingly, the cost of the 1-inch marble would be \( x - 30 \) cents.
Rochelle buys 25 1-inch marbles for a total of $10, which is equivalent to 1000 cents. Therefore, we can set up the following equation:
\[ 25(x - 30) = 1000 \]
Now, we will expand and solve for \( x \):
\[ 25x - 750 = 1000 \]
Adding 750 to both sides gives:
\[ 25x = 1750 \]
Now, divide both sides by 25:
\[ x = 70 \]
Thus, the cost of a 2-inch marble is \( x \) cents, which is 70 cents.
Looking at the provided options, we can conclude:
The cost of a 2-inch marble is $0.70.