Based on the nuclear magnetic resonance NMR spectrum provided, the unknown compound X has a singlet at 7.8 ppm and a triplet at 1.2 ppm. The singlet at 7.8 ppm suggests the presence of an aromatic proton or a proton attached to a carbon with double bond C=C or a carbonyl group C=O . The triplet at 1.2 ppm indicates the presence of a methyl group CH3 adjacent to a methylene group CH2 , as the splitting pattern follows the n+1 rule n = number of neighboring protons .Based on this information, the structure of the unknown compound X could be an aromatic ring with a methyl group CH3 attached to the carbon adjacent to the aromatic proton. Alternatively, it could be a compound with a double bond or carbonyl group adjacent to a methylene group CH2 and a methyl group CH3 .To further narrow down the structure, additional information such as the integration of the peaks, coupling constants, or other spectroscopic data e.g., IR or mass spectrometry would be needed.