Question

1/7+[3/7-(5/28-5/84)]+1/21
Vă rog explicația!!!

Answer 1

1/7+[3/7-(5/28-5/84)]+1/21 =

= 1/7 + (3/7 -5/42) +1/21 =

= 1/7+13/42+1/21 =

=(6+13+2)/42 = 21/42 = 1/2

Answer 2

$\frac{1}{7}+[ \frac{3}{7}-( \frac{5}{28}- \frac{5}{84})]+ \frac{1}{21}= \frac{3}{21}+ \frac{1}{21} + [ \frac{3}{7}-( \frac{15}{84}- \frac{5}{84})] = \frac{4}{21}+( \frac{3}{7}- \frac{10}{84}) =  \frac{16}{84}+ \frac{36}{84}- \frac{10}{84}= \frac{42}{84}= \frac{1}{2}$