Let P be the number of photos in the photo shoot.
After Toby deleted 7 shots, he had 63 - 7 = <<63-7=56>>56 photos.
After taking 15 cat pictures, he had 56 + 15 = <<56+15=71>>71 photos.
After the photo shoot, he had 71 + P photos.
After deleting 3 photos, he had 71 + P - 3 = <<71+-3=68>>68 + P photos.
He had 68 + P = 84 photos in the end.
Thus, Toby took P = 84 - 68 = <<84-68=16>>16 photos in the photo shoot.
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