1 chai dầu nặng là:

\(0,75\times0,8=0,6\left(kg\right)\)

Nửa chai nặng số kg là:

\(0,6:2+0,7=1\left(kg\right)\)

B

taoyêumày xem lại nhé

bt thôi^(hehe)

\(a,0,8\times62,7+36,3\times0,8+0,8\\ =0,8\times\left(62,7+36,3+1\right)\\ =0,8\times100\\ =80\)

\(\dfrac{6}{36}+\dfrac{5}{6}=\dfrac{1}{6}+\dfrac{5}{6}=\dfrac{6}{6}=1\\ \dfrac{1}{4}+\dfrac{5}{30}=\dfrac{1}{4}+\dfrac{1}{6}=\dfrac{6}{24}+\dfrac{4}{24}=\dfrac{10}{24}=\dfrac{5}{12}\\ \dfrac{5}{56}+\dfrac{3}{21}=\dfrac{5}{56}+\dfrac{1}{7}=\dfrac{5}{56}+\dfrac{8}{56}=\dfrac{13}{56}\\\dfrac{12}{18}+\dfrac{12}{42}=\dfrac{2}{3}+\dfrac{2}{7}=\dfrac{14}{21}+\dfrac{6}{21}=\dfrac{20}{21} \)

\(\dfrac{x+\left(x-10\right)}{2}.8=160\\ \dfrac{x+\left(x-10\right)}{2}=160:8\\\dfrac{x+x-10}{2}=20\\ 2x-10=20.2\\ 2x-10=40\\ 2x=40+10\\ 2x=50\\ x=50:2\\ x=25 \)

0 là số thừa à

\(b,4\dfrac{1}{2}x-\dfrac{1}{2}x=\dfrac{2}{3}:\dfrac{4}{9}\\ \dfrac{9}{2}x-\dfrac{1}{2}x=\dfrac{3}{2}\\ \left(\dfrac{9}{2}-\dfrac{1}{2}\right)x=\dfrac{3}{2}\\ 4x=\dfrac{3}{2}\\ x=\dfrac{3}{2}:4\\ x=\dfrac{3}{8}\)