Answer: 20 inches long.
Explanation:
The Rectangular frame which Tamara already has is 3 inches by 5 inches. The larger one happens to be 12 inches by X inches. We can find the scale of the new Frame by dividing the new value we are provided with by the initial one. In this case, 12 (large frame) divided by 3, or 4. This means that the dimensions of the large Frame are 4 times greater than the smaller one. If this is to be the case, the length is 4 times larger than the original, and 5 x 4 = 20.