А) -³/₇ × ⁵/₁₃ -⁴/₇ × ⁵/₁₃ = ⁵/₁₃ × (-³/₇ - ⁴/₇) = ⁵/₁₃ × (-⁷/₇) = ⁵/₁₃ × (-1) = - ⁵/₁₃
б) ³/₅ × ⁷/₉ - ³/₅ × (⁷/₉ - ⁵/₆) = ³/₅ × ((⁷/₉ -(⁷/₉ - ⁵/₆)) = ³/₅ × (⁷/₉ - ⁷/₉ + ⁵/₆) = ³/₅ × ⁵/₆ = ³ˣ⁵/₅ₓ₆ = ³/₆ = ¹/₂ = 0,5
в) ²⁴/₂₅ × ³⁷/₄₃ - ²⁴/₂₅ × (³⁷/₄₃ - ¹⁵/₁₆) = ²⁴/₂₅ × ((³⁷/₄₃ - (³⁷/₄₃ - ¹⁵/₁₆)) =
= ²⁴/₂₅ × (³⁷/₄₃ - ³⁷/₄₃ + ¹⁵/₁₆) = ²⁴/₂₅ × ¹⁵/₁₆ = ²⁴ˣ¹⁵/₂₅ₓ₁₆ = ¹⁸/₁₀ = 1⁸/₁₀ = 1,8