45) q20n: q 0 = 13n q :q8n 11n qq

45) $$\frac{q^{20n} : q^0}{q^{13n} : q^{8n} \cdot q^{11n}} = \frac{q^{20n-0}}{q^{13n-8n} \cdot q^{11n}} = \frac{q^{20n}}{q^{5n} \cdot q^{11n}} = \frac{q^{20n}}{q^{5n+11n}} = \frac{q^{20n}}{q^{16n}} = q^{20n-16n} = q^{4n}$$

Ответ: $$q^{4n}$$