Right now the area is 3 x 10 which is 30 square feet. A doubled area would be 60 square feet. Factors of 60 are 2x30, 3x20, 4x15, 5x12, and 6x10. The only factors that are both bigger than 3 and 10 are 4x15 and 5x12. 5 is 2 bigger than 3 and 12 is 2 bigger than 10, so those are the factors she wants. So she should increase each dimension by 2.