Đáp án + Giải thích các bước giải:
`a) 3/7+5/14-1/2=6/14+5/14-7/14=4/14=2/7`
`b) 21/17*2/7+21/17*5/7-3 4/17 = 21/17(2/7+5/7) - 3 4 /17` $\\$ `= 21/17-3 4/17 = (1-3)-(21/17-4/17)=-2`
`c) 75% + 1 1/2 + 0,4*(-15)/4 + (-1/2)^2` $\\$ `= 3/4+3/2+2/5*(-15)/4+1/4` $\\$ `= 3/4+ 6/4 + 1/1*(-3)/2+1/4` $\\$ `= 9/4 - 3/2 + 1/4 = 10/4 - 3/2` $\\$ `= 5/2 - 3/2 = 2/2 = 1`