Given,

Three-digit number to be formed which are divisible by 3 using the digits 1,3,5,8 and repetition is allowed,

Now taking case , where all digits are same, we get

(1,1,1), (3,3,3), (5,5,5), (8, 8, 8) 4 ways

Now taking case , where 2-digit are same and one is distinct, we get

(5,5, 8) = 3 ways, (8, 8, 5) 3 ways

Now taking case , where all are distinct, we get

(1,3, 5) 6 ways, (1, 8,3) 6 ways

So, total ways will be 4 + 3 + 3 + 6 + 6 = 22

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