3 x 7 = 21 You can put "to the first power" after the three and the seven, but it's not necessary.
The prime factorization of 50 using exponents is 21 x 52
3 x 7 = 21 No exponents necessary.
3 x 7 = 21
21 x 33
10 = 21*51
14 = 21 x 71
21 x 831 = 166
94 = 21 x 471
It is: 21*71*111 = 154
302 = 21 x 1511
142 = 21 x 711
It is: 21*31*431 = 258