Đáp án:a,378/540. b,252/862. c,1260/1548. d,-810/600
Giải thích các bước giải:
a, 6/12+9/45=270/540+108/540=378/540
b,-3/24+6/36=-108/864+144/864=252/862
c,-12/36+21/42=-504/1548+756/1548=1260/1548
d,-18/24+15/-25=-18/24+-15/25=-450/600+-360/600=-810/600