ANSWER
28.3%
Step-by-step explanation
The total number of people that play Equation IQ is 300 - we can know this by adding either the more right column or the lowest row of the table.
From those people, 85 are in grade 6. The probability of a person that plays Equation IQ being in grade 6 is:
To write it as a percentage we just have to multiply it by 100: