Let one part is Rs x Other part is Rs(12000 - x)
One part of investment = \(x\times\frac{10}{100}=\frac{10x}{100}\)
Other part of investment = (12000 - x)\(\times\frac{12}{100}\) = \(\frac{144000-12x}{100}\)
Total investment = 1280
Therefore one part is Rs 8000 and other part is Rs 4000