Atextbook costs $58 and sells for $70. find the rate of markup based on the selling price.

Let's dissect this problem: "A textbook costs $58" Okay, original amount: $58.

"and sells for $70" Okay, new price: $70. "Find rate of markup" Alright!

So to set up the problem, you need to find $58 times some number is $70.

That looks like  this:

$58 * SN = $70

Now divide $70 by $58

SN = 1.21

Now make it a percentage:

121%

Now subtract 100% because it is markup

21%

The markup on the textbook is 21%.

Hope that helps!