Given:
a.) A mobile device that normally sells for $99.90
b.) It was marked down by 10%.
To be able to determine the discount price, we will be using the following formula,
[tex]\text{ Discount Price = Original Price - (Original Price x }\frac{\text{Mark Down Percentage}}{100}\text{)}[/tex]We get,
[tex]\text{ Discount Price = Original Price - (Original Price x }\frac{\text{Mark Down Percentage}}{100}\text{)}[/tex][tex]\text{ = \$99.90 - (\$99.90 x }\frac{10}{100})[/tex][tex]\text{ = \$99.90 - (\$99.90 x }0.10)[/tex][tex]\text{ = \$99.90 - \$9.99}[/tex][tex]\text{ Discount Price = \$89.91}[/tex]Therefore, the discount price is $89.91