Đáp án:
`a)`
` A = ( 1/2 - 7/13 -1/3) + (-6/13 +1/2 + 1 1/3) `
` = 1/2 -7/13 -1/3 -6/13 +1/2 + 4/3`
` = (1/2+1/2) - (7/13+6/13) + (4/3 -1/3)`
` = 1 - 1 + 1 = 1`
`b)`
` B = 0,75 +2/5 + (1/9 - 1 2/5 + 5/4)`
` = 3/4 + 2/5 +1/9 - 7/5 +5/4`
` = (3/4+ 5/4) + (2/5-7/5) + 1/9`
` = 2 + (-1) +1/9`
` = 1 +1/9 = 9/9 +1/9 = 10/9`
`c)`
` C = ( -1 1/2 : 3/4) * ( -4 1/2 - 1/2 )`
` = (-3/2 : 3/4) * (-5)`
` = -2 * (-5)`
` = 10`