Số tiền 15 quyển vở trước khi giảm giá là :

15.7000 = 105 000 ( đồng )

Số tiền 15 quyển vở sau khi giảm giá 10% là :

105 000.90% = 94 500 ( đồng )

Vậy bạn An đem theo 100 000 nên đủ tiền mua 15 quyển vở

a, 1- \(\dfrac{1}{2}\) + \(\dfrac{1}{3}\)

= \(\dfrac{6}{6}\) - \(\dfrac{3}{6}\)+ \(\dfrac{2}{6}\)

= \(\dfrac{5}{6}\)

b, \(\dfrac{2}{5}\) + \(\dfrac{3}{5}\) : \(\dfrac{9}{10}\)

= \(\dfrac{2}{5}\) + \(\dfrac{3}{5}\) . \(\dfrac{10}{9}\)

= \(\dfrac{2}{5}\) + \(\dfrac{3}{45}\)

= \(\dfrac{18}{45}\) + \(\dfrac{3}{45}\)

= \(\dfrac{21}{45}\) = \(\dfrac{7}{15}\)

c, \(\dfrac{7}{11}\) . \(\dfrac{3}{4}\) + \(\dfrac{7}{11}\) . \(\dfrac{1}{4}\) + \(\dfrac{4}{11}\)

=  \(\dfrac{7}{11}\) . (\(\dfrac{3}{4}\) + \(\dfrac{1}{4}\)) + \(\dfrac{4}{11}\)

= \(\dfrac{7}{11}\) . 1 + \(\dfrac{4}{11}\)

= \(\dfrac{7}{11}\) + \(\dfrac{4}{11}\)

= \(\dfrac{11}{11}\) = 1

d, (\(\dfrac{3}{4}\) + 0,5 + 0,25%) . 2\(\dfrac{2}{3}\)

= ( \(\dfrac{3}{4}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{4}\)) . \(\dfrac{8}{3}\)

= ( \(\dfrac{3}{4}\) + \(\dfrac{2}{4}\) + \(\dfrac{1}{4}\)) . \(\dfrac{8}{3}\)

= \(\dfrac{6}{4}\) . \(\dfrac{8}{3}\)

= \(\dfrac{6}{6}\) = 1