First add up the numbers of the three kinds of mutant frog: 5 frogs + 2 frogs + 2 frogs = <<5+2+2=9>>9 frogs
Then add that number to the number of normal frogs to find the total number of frogs: 9 frogs + 18 frogs = <<9+18=27>>27 frogs
Finally, divide the number of mutant frogs by the total number of frogs and multiply by 100% to find the percentage of frogs that are mutants: 9 frogs / 27 frogs * 100% = 33.333...%, which rounds to 33%
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