Answer:
7
Step-by-step explanation:
So, we know that this process happened 3 times in total. The original amount of kids we can call x, so the next wave filled in the gaps inbetween, so we call that amount x-1, the next wave would be (x+x-1)-1 or 2x-2, and the last would be 4x-4
adding this all up we get 8x-7=49, so 8x = 56 or x = 7