$A= 4/7+ 3/4 +2/7 +5/4 +1/7$
$A= (4/7+2/7 +1/7) + ( 3/4+5/4)$
$A=(4 + 2+ 1)/7 + (3+5)/4$
$A= 7/7 +8/4$
$A=1 + 2$
$A= 3$
.
$B= 5/2 +6/11+3/8+7/2+6/8 + 5/11$
$B=( 5/2 +7/2) + (6/11 + 5/11) + (3/8 + 6/8)$
$B= (5+7)/2 + (6+5)/11 + (3+6)/8$
$B= 12/2 + 11/11 + 9/8$
$B= 6 + 1 + 9/8$
$B= 7 + 9/8$
$B= 56/8 + 9/8$
$B = 65/8$
.
$C= 4/3+3/5 +7/3 + 2/5 + 1/3$
C= (4/3 + 1/3 + 7/3) + (3/5 + 2/5)
C= 12/3 + 5/5
C= 4 + 1
C= 5
$D=5/12 + 5/3 +2/12 + 2/3$
$D= (5+2)/12 + (5+2)/3$
$D= 7/12 + 7/3$
$D= 35/12$