Выразите A

01 1) $$ \frac{A}{15} = \frac{9}{5} $$ $$ A = \frac{9 \cdot 15}{5} = 9 \cdot 3 = 27 $$ 2) $$ \frac{9}{4} = \frac{A}{20} $$ $$ A = \frac{9 \cdot 20}{4} = 9 \cdot 5 = 45 $$ 3) $$ \frac{4}{1.8} = \frac{5}{A} $$ $$ A = \frac{5 \cdot 1.8}{4} = \frac{9}{4} = 2.25 $$ 4) $$ \frac{12}{A} = \frac{6}{7} $$ $$ A = \frac{12 \cdot 7}{6} = 2 \cdot 7 = 14 $$ 02 1) $$ A : 0.5 = 4 : 15 $$ $$ A = \frac{4 \cdot 0.5}{15} = \frac{2}{15} $$ 2) $$ 7 : 3.6 = A : 1.44 $$ $$ A = \frac{7 \cdot 1.44}{3.6} = \frac{7 \cdot 1.44}{3.6} = 7 \cdot 0.4 = 2.8 $$ 3) $$ 2 : 0.75 = 0.8 : A $$ $$ A = \frac{0.8 \cdot 0.75}{2} = 0.4 \cdot 0.75 = 0.3 $$ 4) $$ 0.9 : A = 1.2 : 7 $$ $$ A = \frac{0.9 \cdot 7}{1.2} = \frac{0.3 \cdot 7}{0.4} = \frac{2.1}{0.4} = 5.25 $$ 03 1) $$ \frac{A}{3} = 2\frac{1}{3} $$ $$ A = 3 \cdot 2\frac{1}{3} = 3 \cdot \frac{7}{3} = 7 $$ 2) $$ 1\frac{3}{4} = \frac{1}{A} $$ $$ \frac{7}{4} = \frac{1}{A} $$ $$ A = \frac{4}{7} $$ 3) $$ 0.25 : 1.4 = \frac{3}{4}A $$ $$ \frac{1}{4} : 1.4 = \frac{3}{4}A $$ $$ A = \frac{\frac{1}{4}}{\frac{3}{4} \cdot 1.4} = \frac{1}{3 \cdot 1.4} = \frac{1}{4.2} = \frac{10}{42} = \frac{5}{21} $$ 4) $$ 7 = \frac{2.1}{A} $$ $$ A = \frac{2.1}{7} = 0.3 $$ 04 1) $$ \frac{3y}{2} = \frac{1}{7A+1} $$ $$ 7A+1 = \frac{2}{3y} $$ $$ A = \frac{\frac{2}{3y}-1}{7} = \frac{2-3y}{21y} $$ 2) $$ \frac{1}{A+x} = 4 : 1.8 $$ $$ \frac{1}{A+x} = \frac{4}{1.8} = \frac{40}{18} = \frac{20}{9} $$ $$ A + x = \frac{9}{20} $$ $$ A = \frac{9}{20} - x $$ 3) $$ \frac{y}{A} + 1 = \frac{9}{4} $$ $$ \frac{y}{A} = \frac{9}{4} - 1 = \frac{5}{4} $$ $$ A = \frac{4y}{5} $$ 4) $$ \frac{1}{2A-3} = \frac{x}{2} - 1 $$ $$ \frac{1}{2A-3} = \frac{x-2}{2} $$ $$ 2A-3 = \frac{2}{x-2} $$ $$ A = \frac{\frac{2}{x-2} + 3}{2} = \frac{2+3(x-2)}{2(x-2)} = \frac{2+3x-6}{2(x-2)} = \frac{3x-4}{2(x-2)} $$