\(\left(\frac{3}{7}\right)^{21}:\left(\frac{9}{49}\right)^6=\frac{3}{7}.\left(\frac{3}{7}\right)^{20}:\left(\frac{9}{49}\right)^6=\frac{3}{7}.\left(\frac{3^2}{7^2}\right)^{10}:\left(\frac{9}{49}\right)^6\\ =\frac{3}{7}.\left(\frac{9}{49}\right)^{10}:\left(\frac{9}{49}\right)^6=\frac{3}{7}.\left(\frac{9}{49}\right)^4=\frac{3}{7}.\left(\frac{3^2}{7^2}\right)^6\)

\(\frac{3}{7}.\left(\frac{3}{7}\right)^{12}=\left(\frac{3}{7}\right)^{13}\)

Talk about your family:

- Hi everyone. My name's Nguyen. I'm a student at Tran Phu Secondary School. I'm in grade 7. My family has five people: My grandma, my parents, my sisters and me. My grandma is 70 years old so she is very old. My father is 45 years old and he is an inspector. My mother is 38 years old, she is a teacher. My sisters and me are students. My sisters are very friendly. We live very happily in a peaceful town.