log₁₅ 5 + log₁₅3 = log₁₅(3·5) = log₁₅15 = 1
log₁/₆ 4 + log₁/₆ 9 = log₁/₆ (4·9) = log₁/₆ 36 = -2
log₉ 45 + log₉ 1.8 = log₉(45·1.8) = log₉81 = 2
log₄ 192 - log₄ 3 = log₄ (192 : 3) = log₄ 64 = 3
log₂ 13 - log₂ 1 5/8 = log₂ (13 : 1 5/8) = log₂ (13 : 13/8) = log₂ 8 = 3
log₃ 9¹⁰ = 10log₃ 9 = 10 · 2 = 20