[tex]\displaystyle\bf\\\Big(2^{53}+2^{52}+2^{51}\Big):\Big(2^{17}\Big)^3=\\\\\\=\frac{\Big(2^{53}+2^{52}+2^{51}\Big)}{\Big(2^{17}\Big)^3}=\\\\\\=\frac{\Big(2^{51+2}+2^{51+1}+2^{51}\Big)}{2^{17\times3}}=\\\\\\=\frac{\Big(2^{51}\times2^2+2^{51}\times2^1+2^{51}\Big)}{2^{51}}=\\\\\\=\frac{2^{51}\Big(4+2+1\Big)}{2^{51}}=4+2+1=\boxed{\bf7}[/tex]