The given measurement of the Instagram photo is "4" by "4". And a poster enlargement is being printed with a scale factor of 8.5 .
So on using the scale factor of 8.5 , lengths of new sides are "8.5 *4" by "8.5 *4"
= " 34" by "34" .
So the new lengths of the enlarged pictures are of dimension "34" by "34" .