To find the marginal relative frequency of children who were surveyed from a two-way relative frequency table, you would typically look at the total percentage for the children category across all groups.
However, since I do not have the actual two-way relative frequency table, I cannot compute the exact marginal relative frequency. If you have the frequencies shown in the table, you would sum the relative frequencies (percentages) associated with children across different categories and then interpret that sum as the marginal relative frequency of the children surveyed.
Please provide the relevant data from the table to enable me to assist further!