найдите значение выражения -4 5/7+(-1 6/7) ; -4 5/+(-4/7) ; -5/18+(-4/45) ; -4 9/14+(-3 4/21) помогите

а)-45/7-16/7= -45-16/7 = -61/7

б) -45/7-4/7 = -45-4/7= -49/7= -7

в) -5/18-4/45 =-(5/18+4/45)= -(5×5/18×5 + 4×2/45×2) = -(25/90 + 8/90)= - 25+8/90 = -33/90 = -11/30

г) -49/14-34/21= -(7/2+34/21)= -(7×21/2×21+34×2/21×2)= -(147/42+68/42) = - 147+68/42= - 215/42