ANSWER
28.3%
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:
[tex]P(\text{grade 6})=\frac{\#\text{ people in grade 6}}{\#\text{ total number of players}}=\frac{85}{300}\approx0.2833\ldots[/tex]
To write it as a percentage we just have to multiply it by 100:
[tex]0.283\times100=28.3\text{ \%}[/tex]
