8<8,2

Có tất cả 1 góc đỉnh Y

a,\(\dfrac{3}{5}+\dfrac{1}{3}=\dfrac{9}{15}+\dfrac{5}{15}=\dfrac{14}{15}\)
b,\(\dfrac{17}{20}-\dfrac{4}{5}=\dfrac{17}{20}-\dfrac{16}{20}=\dfrac{1}{20}\)
c,\(\dfrac{25}{35}\)x\(\dfrac{4}{5}=\dfrac{4}{7}\)
d,\(\dfrac{7}{15}:\dfrac{6}{7}=\dfrac{7}{15}\)x\(\dfrac{7}{6}=\dfrac{49}{90}\)
 

lỗi

a,\(=\dfrac{5}{3}\)và\(\dfrac{6}{3}\)
b,\(=\dfrac{63}{36}\)và\(\dfrac{56}{36}\)
c,\(=\dfrac{9}{6}\)và\(\dfrac{10}{6}\)

lỗi

a,

b, 
X=\(\dfrac{5.4+7.3+8.8+9.8+10.4+14.3}{30}\)
X=\(\dfrac{259}{30}\)
Mo=8;9