[tex]12.(3) \times 2.25 - 5 \frac{1}{2} \div 4 \frac{2}{5} = \\ \\ = 12 \frac{3}{9} \times \frac{225}{100} - \frac{5 \times 2 + 1}{2} \div \frac{4 \times 5 + 2}{5} = \\ \\ = \frac{12 \times 9 + 3}{9} \times \frac{9}{4} - \frac{11}{2} \div \frac{22}{5} = \\ \\ = \frac{111}{9} \times \frac{9}{4} - \frac{11}{2} \times \frac{5}{22} = \\ \\ = \frac{111}{1} \times \frac{1}{4} - \frac{1}{2} \times \frac{5}{2} = \\ \\ = \frac{111}{4} - \frac{5}{4} = \\ \\ = \frac{106}{4} = \frac{53}{2} [/tex]
