What is the total cost of a $150.00 necklace if the sales tax is 6.5%

The best thing to do is to find what 1% is, and you can do this by dividing 150 by 100.
150/100= 1.5
As you're looking for 6.5%, you've got to multiply 1.5 by 6.5
1.5*6.5= 9.75
You've then got to add 9.75 and 150 together
150+9.75= $159.75
Therefore, after the sales tax, the cost of the necklace is $159.75 
Hope this helps :)