Let
x--------------> the number of slices eating by Consuela and her three friends
we know that
[total slices]=8*2=16 slices
[slices of pizza for her older brother]=2
x=16-2=14 slides
Consuela and her friends share the rest of the pizza, each eating the same number of slices---------> 14/4= 3.5 slides of pizza each (this part is not necessary, but it is shown in a didactic way)
the question is
What fraction of the 2 pizzas is left over?
[slices of pizza for her older brother]/[total slices]=2/16=1/8
the answer is (1/8)