If he eat 6 apples in 2 days so we can say he eat 3 apple in 1 day so if we want to know in how many days he can eat 51 apple you can say 51 ÷ 3= 17 also we can say 1day / 3 apples = ? days / 51 apples ⇒ 51×1 / 3 = 17 so he can eat 51 apples in 17 days :)))) i hope this be helpful * happy new year *