In the equation \(0.3 \times 0.4 = 0.12\), the answer \(0.12\) represents the portion of the books in the library that are how-to books on electronics.
This is calculated by taking 0.3 (the portion of all books that are how-to books) and multiplying it by 0.4 (the portion of how-to books that deal with electronics), resulting in 0.12, which indicates that 12% of the total books in the library are how-to books specifically about electronics.