Isobel adds it up

Isobel is a problem solver.addition, subtraction, multiplication, division! But trying to figure out who is causing all the noise next door is one problem she can't quite work out. Is it a marching band? A basketball team in the middle of a practice? Could it be a family of elephants? Isobel doesn't know what to do about all the noise, but the solution just might come from the most unlikely place!