How do outliers affect a box and whisker plot?
Outliers are important because they are numbers that are "outside" of the Box Plot's upper and lower fence, though they don't affect or change any other numbers in the Box Plot your instructor will still want you to find them.
If you want to find your fences you will first take your IQR and multiply it by 1.5. I call this your "magic number".
Lower fence: Take your Q1 and subtract it from your magic number, that number your get is your lower fence.
Upper fence: Take your Q3 and add it to your magic number, that number you get is your upper fence.
Remember, any numbers that are "outside" the lower or upper fences is considered an outlier.