Of course, i think i want to play a game for fun. Because it helps me to relax and good for my happiness.

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Sửa bài:

   Đặt biểu thức là A. ta được:

     \(\dfrac{A}{5}=\dfrac{5}{1.6}+\dfrac{5}{6.11}+...+\dfrac{5}{26.31}\\ \dfrac{A}{5}=1-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{11}+...+\dfrac{1}{26}-\dfrac{1}{31}\\ \dfrac{A}{5}=\dfrac{30}{31}\\ A=\dfrac{150}{31}.\)

\(\dfrac{5^2}{1.6}+\dfrac{5^2}{6.11}+...+\dfrac{5^2}{26.31}\\ =5^2\left(\dfrac{1}{1.6}+\dfrac{1}{6.11}+...+\dfrac{1}{26.31}\right)\\ =5^2.\left(1-\dfrac{1}{6}+\dfrac{1}{6}+...+\dfrac{1}{26}-\dfrac{1}{31}\right)\\ =5^2.\left(1-\dfrac{1}{31}\right)\\ =5^2.\dfrac{30}{31}\\ =25.\dfrac{30}{31}\\ =\dfrac{750}{31}.\)

\(3\left(x-2\right)=-100+211\\ 3\left(x-2\right)=111\\ x-2=37\\ x=39.\)

\(y:84=\dfrac{106}{84}\\ y=\dfrac{106}{84}\times84\\ y=106.\)

\(6\times\left(15+5x\right)=300\\ 15+5x=50\\ 5x=35\\ x=7.\)

B.smoked

\(a,\left(x-12,7\right):0,48=427,5\\ x-12,7=205,2\\ x=217,9\\ b,20,49+x=7,25\times6,28\\ 20,49+x=45,53\\ x=25,04.\)

\(a,19,5-x\times6,3=11,625\\ x\times6,3=7,875\\ x=1,25.\\ b,4,75+x:9,4=34,266\\ x:9,4=29,516\\ x=277,4504.\)