Вопрос по математике: с 9 по 12

9)-12÷(-6/7)=12÷6/7=12×7/6=2×7/1=14/1=14 10)-3/4÷(-5)=3/4÷5=3/4×1/5=3/20 11)-1 8/27÷(-1 5/9)=1 8/27÷1 5/9=35/27÷14/9=35/27×9/14=5/3×1/2=5/6 12)-3 3/26÷(-2 10/13)=81/26÷36/13=81/26×13/36=9/2×1/4=9/8=1 1/8