The frog eats 2 flies/day * 7 days/week = <<2*7=14>>14 flies a week.
Betty catches flies in the morning and in the afternoon, for a total of 5 flies + 6 flies = <<5+6=11>>11 flies.
But 1 fly escapes, leaving 11 flies - 1 fly = <<11-1=10>>10 flies.
To get her frog's food for the whole week, Betty needs 14 flies - 10 flies = <<14-10=4>>4 more flies.
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