A = \(\dfrac{1}{2}\) - \(\dfrac{1}{3.7}\) - \(\dfrac{1}{7.11}\) - \(\dfrac{1}{11.15}\) - \(\dfrac{1}{15.19}\) - \(\dfrac{1}{19.23}\) - \(\dfrac{1}{23.27}\)

A = \(\dfrac{1}{2}\) - ( \(\dfrac{1}{3.7}\) + \(\dfrac{1}{7.11}\) + \(\dfrac{1}{11.15}\) + \(\dfrac{1}{15.19}\) + \(\dfrac{1}{19.23}\) + \(\dfrac{1}{23.27}\))

A = \(\dfrac{1}{2}\) - \(\dfrac{1}{4}\).( \(\dfrac{4}{3.7}\) + \(\dfrac{4}{7.11}\) + \(\dfrac{4}{11.15}\) + \(\dfrac{4}{15.19}\) + \(\dfrac{4}{19.23}\) + \(\dfrac{4}{23.27}\))

A = \(\dfrac{1}{2}\) -\(\dfrac{1}{4}\) .( \(\dfrac{1}{3}\) - \(\dfrac{1}{7}\) + \(\dfrac{1}{7}\) -  \(\dfrac{1}{11}\)+ \(\dfrac{1}{11}\)- \(\dfrac{1}{15}\) +\(\dfrac{1}{15}\)-\(\dfrac{1}{19}\) +\(\dfrac{1}{19}\) - \(\dfrac{1}{23}\) + \(\dfrac{1}{23}\) - \(\dfrac{1}{27}\))

A =  \(\dfrac{1}{2}\) - \(\dfrac{1}{4}\). ( \(\dfrac{1}{3}\) - \(\dfrac{1}{27}\))

A = \(\dfrac{1}{2}\) - \(\dfrac{1}{4}\). \(\dfrac{8}{27}\)

A = \(\dfrac{1}{2}\) - \(\dfrac{2}{27}\)

A = \(\dfrac{23}{54}\)

-2x + 0,25 = -x - 0,5

0,25 + 0,5 = -x + 2x

0,75 = x 

Vậy x = 0,75

-2x + 0,25 = -x-0,5
-2x + x       = -0,5 - 0,25
-x               = -0,75
 x               = 0,75
           Vậy x = 0,75

Số tiền mẹ An phải trả là:

   (8000000 + 300000) x (100% - 20%) = 6640000 (đồng)

\(\dfrac{2}{5}x-\dfrac{1}{5}=-0,6\\ =>\dfrac{2}{5}x-\dfrac{1}{5}=-\dfrac{3}{5}\\ =>\dfrac{2}{5}x=-\dfrac{3}{5}+\dfrac{1}{5}\\ =>\dfrac{2}{5}x=-\dfrac{2}{5}\\ =>x=-\dfrac{2}{5}:\dfrac{2}{5}\\ =>x=-1\)

2/5x - 1/5 = -0,6

2/5x - 1/5 = -3/5

2/5x         = -3/5 + 1/5

2/5x         = -2/5

    x          = -2/5 : 2/5

    x          = -10/10 = -1

2⁷ x 9² x 2022⁰/3⁵ x 8²

= 2⁷ x 3⁴ x 1/3⁵ x 2⁶

= 2/3

mn giúp mình vời, mình cần gấp