What is the sales tax on a breakfast order that totals $10.50 when tax is 5%

First, you would need to create an equation for this problem. Let x represent the unknown tax. 
=

Next, you would cross multiply. 
100x = 52.5

Now, all you would have to do is isolate the x. To do this, you would divide both sides by 100. 
x = $0.525

I hope this helps!