Answer:
Let
x---------> the number of 6-inch pies Annika sold
y--------> the number of 8-inch pies Annika sold
we know that
x=2y------> equation 1
5x+9y=133---> equation 2
substitute the equation 1 in equation 2
5*[2y]+9y=133
10y+9y=133
19y=133
y=7
x=2y-----> x=2*7-----> x =14