12,345=10+2+0,3+0,04+0,005

(9x-2³):5=2

⇒(9x-8):5=2

⇒9x-8=2.5=10

⇒9x=10+8=18

⇒x=18:9

⇒x=2

Số còn lại là: 75x2-65=85

         Đ/S: 85

\(\dfrac{12}{5}\cdot\dfrac{5}{9}-\dfrac{1}{3}=\dfrac{4}{3}-\dfrac{1}{3}=1\)

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\(\left(5^7+7^5\right)\cdot\left(6^8+8^6\right)\cdot\left(2^4-4^2\right)\\ \\ \\ \\ =\left(5^7+7^5\right)\cdot\left(6^8+8^6\right)\cdot\left(16-16\right)\\ \\ \\ \\ =\left(5^7+7^5\right)\cdot\left(6^8+8^6\right)\cdot0=0\)

\(\dfrac{3}{2}\text{x}\dfrac{4}{7}\text{x}\dfrac{2}{4}=\dfrac{3\text{x}4\text{x}2}{2\text{x}7\text{x}4}=\dfrac{3}{7}\)

\(\dfrac{5}{3}\text{x}\dfrac{4}{7}\text{x}\dfrac{3}{5}\text{x}\dfrac{7}{8}=\dfrac{5\text{x}4\text{x}3\text{x}7}{3\text{x}7\text{x}5\text{x}8}=\dfrac{4}{8}=\dfrac{1}{2}\)