= 17/7 + 4/7 - 2/5 + 3/5

= 21/7 - 5/5

= 3 - 1

= 2

3/2 + 4/9 + 4/7 + 5/9 = 43/14

  1+2+3+4+5+6+7+8+9:9

=1+2+3+4+5+6+7+8+1

=(1+1)+(2+8)+(3+7)+(4+6)+5

=2+10+10+10+5

=(2+5)+(10+10+10)

=7+30

=37

1 + 2 +  3 + 4 + 5 + 6 + 7 + 8 + 9 : 9

= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5 : 9

=      10    +      10     +     10      +     10     + 5 : 9

=             20              +              20             + 5 : 9

=                              40                              + 5 : 9

=                                                  45                : 9

=                                                                5

\(a,\dfrac{5}{9}\times\dfrac{5}{2}+\dfrac{4}{9}\times\dfrac{5}{2}=\dfrac{5}{2}\times\left(\dfrac{5}{9}+\dfrac{4}{9}\right)=\dfrac{5}{2}\times1=\dfrac{5}{2}\)

\(12\times\dfrac{3}{4}-\dfrac{3}{4}\times\dfrac{12}{7}=\dfrac{3}{4}\times\left(12-\dfrac{12}{7}\right)=\dfrac{3}{4}\times\dfrac{72}{7}=\dfrac{54}{7}\)

3/7.5/6+4/7.5/6

= 5/6.(3/7+4/7)

=5/6.1

=5/6

3/7*5/6+4/7*5/6

=5/6*(3/7+4/7)

=5/6*1

=5/6

7/9 x 5/16 : 5/9 x4/7

=7/9 x 5/16 x9/5 x 4/7

=7/9 x 45/80 x 4/7 

=7/9 x 9/16 x 4/7

=7 x 9 x 4 /9 x 16 x 7

=1/4

2/3 *  10/21 * 3/2 = (2/3 * 3/2) * 10/21 = 1 * 10/21 = 10/21

22/5 * 12 * 5/12 = 22/5 * (12 * 5/12) = 22/5 * 5 =22

7/2 * 28/81 * 2/7= (7/2 * 2/7) * 28/81 = 1 * 28/81 =28/81

5/17 * 21/4 * 47/15 * 0 = 0

~Study well~

#Seok_Jin#

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