 
<translate> Idan 1st mafi sauri kare ne 10 shekara, da kuma 2nd mafi sauri kare ne 2 shekaru matasa fiye da na farko mafi sauri kare, da 2nd mafi sauri kare ne 10 - 2 = 8 shekara. Kare na uku mafi sauri yana da shekaru 4 da ya fi kare na biyu mafi sauri, yana da shekaru 8 + 4 = 12. Kare na 4 mafi sauri shine rabin shekarun kare na 3 mafi sauri, ma'ana kare na 4 mafi sauri shine 1 / 2 * 12 = 6 shekaru. Kare na biyar mafi sauri ya fi kare na huɗu sauri da shekaru 20, ma'ana kare na biyar mafi sauri yana da shekaru 6 + 20 = 26. Jimlar shekarun karnuka mafi sauri na 1 da na 5 shine 26 + 10 = shekaru 36. Matsakaicin shekarun karnuka mafi sauri na 1 da na 5 shine 36 / 2 = shekaru 18. Amsar ita ce: 18. <eng> If the 1st fastest dog is 10 years old, and the 2nd fastest dog is 2 years younger than the first fastest dog, the 2nd fastest dog is 10 - 2 = 8 years old. The 3rd fastest dog being 4 years older than the 2nd fastest dog, is 8 + 4 = 12 years old. The 4th fastest dog is half the age of the 3rd fastest dog, meaning the 4th fastest dog is 1 / 2 * 12 = 6 years old. The 5th fastest dog is 20 years older than the 4th fastest dog, meaning the 5th fastest dog is 6 + 20 = 26 years old. The total age of the 1st and 5th fastest dogs is 26 + 10 = 36 years. The average age of the 1st and 5th fastest dogs is 36 / 2 = 18 years old.
The answer: 18. 