The steps to encrypt “Hello. How are you?” with paper and pencil

The steps to encrypt “Hello. How are you?” with paper and pencil.

Plaintext Letter      Plaintext Number    +   Key    Result    Subtract26?    Result    Ciphertext Letter
H                            7                              +   13       = 20                               = 20                20 = U
E                             4                              +   13      = 17                               = 17                17 = R
L                             11                           +    13      = 24                               = 24                24 = Y
L                             11                           +    13      = 24                               = 24                24 = Y
O                            14                            +   13      = 27            - 26             = 1                  1 = B

H                           7                              +    13      = 20                               = 20                 20 = U
O                           14                            +    13      = 27            - 26            = 1                    1 = B
W                          22                            +    13      = 35            - 26            = 9                     9 = J

A                          0                               +    13      = 13                              = 13                   13 = N
R                          17                             +    13      = 30            - 26            = 4                      4 = E
E                           4                              +    13      = 17                              = 17                     17 = R

Y                         24                             +    13      = 37             - 26            = 11                     11 = L
O                         14                             +    13      = 27             - 26            = 1                     1 = B
U                         20                             +    13      = 33             - 26            = 7                      7 = H


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