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\(a,\dfrac{7}{9}-\dfrac{2}{7}+\dfrac{2}{3}+\dfrac{4}{7}\\ =\left(\dfrac{7}{9}+\dfrac{6}{9}\right)+\left(\dfrac{4}{7}-\dfrac{2}{7}\right)\\ =\dfrac{13}{9}+\dfrac{2}{7}\\ =\dfrac{109}{63}\\ b,13,8+7-5,25+4,25\\ =\left(13,8+7\right)-\left(5,25-4,25\right)\\ =20,8-1\\ =19,8\)
a)\(\frac{7}{9}-\frac{3}{7}+\frac{2}{3}-\frac{4}{7}\)
\(=\frac{7}{9}+\frac{-3}{7}+\frac{2}{3}+\frac{-4}{7}\)
\(=\left(\frac{7}{9}+\frac{2}{3}\right)+\left(\frac{-3}{7}+\frac{-4}{7}\right)\)
\(=\frac{13}{9}-1\)
\(=\frac{4}{9}\)
b)13,8 + 7 - 5,25 + 4,25
=(13,8 + 7 + 4,25 ) - 5,25
=25,05 - 5,25
=19,8
a) 7/9 - 3/7 + 2/3 - 4/7
= 7/9 - 3/7 + 6/9 - 4/7
=( 7/9 - 6/9 ) + ( 3/7 + 4/7 )
= 1/9 + 1
=10/9
b) 13,8 + 7 - 5,25 + 4,25
=(13,8 + 7 ) - (5,25 + 4,25 )
=20,8 - 9,5
= 11,3
a) 3 2/7 - 2/5 + 5/7 - 3/5
= 3 + 2/7 - (2/5 + 3/5) + 5/7
= 3 + (2/7 + 5/7) - 1
= 3 + 1 - 1
= 3
b) 5 4/7 - 4/9 + 1 3/7 - 5/9
= 5 + 4/7 - 4/9 + 1 + 3/7 - 5/9
= (5 + 1) + (4/7 + 3/7) - (4/9 + 5/9)
= 6 + 1 - 1
= 6
a) \(3\dfrac{2}{7}-\dfrac{2}{5}+\dfrac{5}{7}-\dfrac{3}{5}\)
\(=\left(\dfrac{23}{7}+\dfrac{5}{7}\right)-\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\)
\(=4-1\)
\(=3\)
b) \(5\dfrac{4}{7}-\dfrac{4}{9}+1\dfrac{3}{7}-\dfrac{5}{9}\)
\(=\left(\dfrac{32}{7}+\dfrac{10}{7}\right)-\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)
\(=6-1\)
\(=5\)
a)7.(90+9+1)
=7.100
=700
b)3/4.(3/9+2/3)
=3/4.1
=3/4
a) ( 36 + 54 ) x 7 + 7 x 9 + 7
= ( 36 + 54 + 9 + 1 ) x 7
= 100 x 7
= 700
b) \(\frac{3}{4}\times\frac{3}{9}+\frac{3}{4}\times\frac{2}{3}\)
\(=\left(\frac{3}{9}+\frac{2}{3}\right)\times\frac{3}{4}\)
\(=1\times\frac{3}{4}\)
\(=\frac{3}{4}\)
a; \(\dfrac{7}{9}\) - \(\dfrac{3}{7}\) + \(\dfrac{2}{3}\) - \(\dfrac{4}{7}\)
= (\(\dfrac{7}{9}\) + \(\dfrac{2}{3}\)) - (\(\dfrac{3}{7}\) + \(\dfrac{4}{7}\))
= \(\dfrac{13}{9}\) - 1
= \(\dfrac{4}{9}\)
b; 13,8 + 7 - 5,25 + 4,25
= (13,8 + 7) - (5,25 - 4,25)
= 20,8 - 1
= 19,8