Answer
a) GR QRW SDVV JR.
b) QB ABG CNFF TB.
c) QX UXM AHJJ ZX.
Work Step by Step
a) We need to replace each letter by the letter three places later in the alphabet. Thus D becomes G, 0
becomes R, and so on. The resulting message is GR QRW SDVV JR.
b) We need to replace each letter by the letter 13 places later in the alphabet. Thus D becomes Q, 0 becomes
B (we cycle, with A following Z), and so on. The resulting message is QB ABG CNFF TB.
c) This one is a little harder, so it is probably easiest to work with the numbers. For D we have p = 3 because
D is the fourth letter of the alphabet. Then 3 · 3 + 7 mod 26 = 16, so the encrypted letter is the 17th letter,
or Q (remember that we start the sequence at 0). Our original message has the following numerical values:
3-14 13-14-19 15-0-18-18 6-14. Multiplying each of these numbers by 3, adding 7, and reducing modulo 26
gives us 16-23 20-23-12 0-7-9-9 25-23. Translating back into letters we have QX UXM AHJJ ZX.
