Old weight = [tex]123 \frac{1}{4} = \frac{493}{4} [/tex]
New weight = [tex]120 \frac{1}{2} = \frac{241}{2} [/tex]
Hence, weight lost = [tex] \frac{493}{4} - \frac{241}{2} = \frac{493-2*241}{4} = \frac{493-482}{4} = \frac{11}{4} = 2 \frac{3}{4} [/tex]
Hence, the answer is [tex]2 \frac{3}{4} [/tex] pounds.