a)8/5-18/27=216/135-90/135=126/135
b)3/5-1/3=9/15-5/15=4/15(rút gọn p/s)
c)1/3-1/5=5/15-3/15=2/15
d)6/7-12/27=162/189-84/189=78/189
a) 8/5 - 18/27
= 8/5 - 2/3
= 24/15 - 10/15
= 14/15
b) 12/20 - 6/18
= 3/5 - 1/3
= 9/15 - 5/15
= 4/15
c) 8/24 - 5/25
= 1/3 - 1/5
= 5/15 - 3/15
= 2/15
d) 18/21 - 12/27
= 6/7 - 4/9
= 54/63 - 28/63
= 26/63