Answer:
Step-by-step explanation:
Prime factorize 12 , 28 , 21 and 16
12 = 2 * 2 * 3 = 2² * 3
28 = 2 * 2 * 7 = 2² *7
21 = 3 * 7
16 = 2 * 2 * 2 * 2 = 2⁴
[tex]\dfrac{12^{7}*28^{6}}{21^{7}*16^{6}}=\dfrac{(2^{2}*3)^{7}*(2^{2}*7)^{6}}{(3*7)^{7}*(2^{4})^{6}}\\\\\\\\=\dfrac{2^{2*7}*3^{7}*2^{2*6}*7^{6}}{3^{7}*7^{7}*2^{4*6}}\\\\\\=\dfrac{2^{14}*3^{7}*2^{12}*7^{6}}{3^{7}*7^{7}*2^{24}}\\\\\\=\dfrac{2^{14+12-24}*3^{7-7}}{7^{7-6}}\\\\\\=\dfrac{2^{2}*3^{0}}{7^{1}}\\\\\\=\dfrac{2^{2}}{7}[/tex]
Hint:
[tex]a^{m}*a^{n}=a^{m+n}\\\\\\(a^{m})^{n}=a^{m*n}\\\\\dfrac{a^{m}}{a^{n}}=a^{m-n} \ if \ m >n\\\\\\\dfrac{a^{m}}{a^{n}}=\dfrac{1}{a^{n-m}} \ if \ n>m[/tex]
