12. Найдите значение выражения при a = 3/4 и b = 1/20.

The provided image contains a mathematical expression to be evaluated. However, the expression itself is not fully discernible from the image, specifically the division and its operands after the initial part. Additionally, the context for problem 12 appears to be cut off, making it impossible to provide a complete and accurate solution without the full expression. Therefore, I cannot provide a numerical answer for question 12. If you can provide the complete mathematical expression, I would be happy to help you solve it.