Use the encrypting congruence c ≡ (7p + 12) mod 26 to code the message parallel lines.

 PARALLEL LINES  should be coded as "TSHSRRUR RWFUO"

Step-by-step explanation:

Since we have given that

PARALLEL LINES

As we know that according to alphabets,

P is at 16

A is at 1

R is at 18

L is at 12

E is at 5

N is at 14

S is at 19

And we have given that

So, P becomes :

A becomes

S becomes

L becomes

E becomes

I becomes

N becomes

R becomes

Hence, PARALLEL LINES  should be coded as "TSHSRRUR RWFUO"

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-12 -5(x + 4) = 3x

-12 - 5x - 20 = 3x

-12 - 20 - 5x = 3x

-32 - 5x = 3x

    + 5x   + 5x

-32 = 8x

8         8

- 4= x