a,
(14,17-y) x 2/9= 1/3
14,17-y = 1/3:2/9
14,17-y= 3/2
14,17-y= 1,5
y= 14,17-1,5
y= 12,67
Vậy y=12,67
b, 2,85 x156,23 - 2,85 x56,23
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2,1+2,4+2,7+3+3,3+3,6+3,9+4,2
= 2,85x(156,23-56,23)
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(2,1+3,9)+(2,4+3,6)+(2,7+3,3)+3+4,2
= 285/25,2
=475/42
d, H = 128/256 +64/256+32/256+16/256+8/256+4/256+2/256+1/256
=128+64+32+16+8+4+2+1/256
=255/256
Sorry nha mk ko biet lam phan c)