Final answer:
Omar has to pay a total of $84 for the pair of shoes, including the GST.
Step-by-step explanation:
To find the total amount Omar has to pay, we need to add the selling price with the GST. The selling price is $80 and the GST is 5% of the selling price. To calculate the GST, we multiply the selling price by 0.05 (since 5% is equivalent to 0.05 in decimal). So, the GST is $80 * 0.05 = $4.
Now, to find the total amount Omar has to pay, we add the selling price and the GST together. $80 + $4 = $84.
Therefore, Omar has to pay a total of $84.
Learn more about Calculating total cost with GST