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If you say 21 is correct then the image math is incorrect.

Horse is 10
10 + 10 +10 = 30

Yellow is 4

10 + 4 + 4 = 18

Silver is 2

4 - 2 = 2

2 + 10 × 4 = 42

Because in the rule of mathematics in (bodmas). Multiplication before addition.

just check the no of shoes and yellow mark asked in the contest, you will automatically get your answer.

I got it. Thanks for shedding more light. Thumbs up.