а) ( \frac{2}{3} \times x - \frac{5}{2} \times x = \frac{2x}{3} - \frac{5x}{2} = \frac{4x}{6} - \frac{15x}{6} = \frac{4x - 15x}{6} = \frac{-11x}{6} )

б) ( x \times \frac{5y}{1} + \frac{3x}{4y} = \frac{5xy + 3x^2}{4y} )

в) ( 4 \times \frac{7a}{1} - 3 \times \frac{5a}{1} = \frac{28a - 15a}{1} = 13a )

г) ( b \times \frac{1}{6a} + 5 \times \frac{b}{7a} = \frac{b}{6a} + \frac{5b}{7a} = \frac{7b + 30b}{42a} = \frac{37b}{42a} )