1 5/14-9/10=19/14-9/10=
=95/70-63/70=32/70=16/35
2.4÷16/35=2 2/5÷16/35=
=12/5÷16/35=12/5×35/16=21/4=
=5 1/4=5.25
9х^2-12x-6x+8=6x^2-2x+9x-3+3x^2-12x+x-4
9x^2-18x+8=9x^2-5x-7
-18x+5x=-8-7
-13x=-15
x=15/13
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