calculate the value of k in this quality
7x7x $7^{6}$ = $7^{k}$
14:35=2:14
14:35=6:15
$$\sum_{i=1}^{n}{2^i+i=3n}$$
Rewrite (4x^3+x)√(4x^2+1)
14:35=20:21
14:35=1:10
6:18=9:45
