Q: Compute 7^3 mod 10 and find the day of the week 100 days after Monday. 7² = 49 ≡ 9; 7³ ≡ 9×7 = 63 ≡ 3 (mod 10). Answer: 3. 100 mod 7: 100 = 14×7+2, so 100 ≡ 2. Monday + 2 = Wednesday! (Clock arithmetic on 7 days.)