An item costs $390 before tax, and the sales tax is $19.50.
Find the sales tax rate.

Write your answer as a percentage.

Answer this question only if you know the answer! 30 points and

The magnitude, m, of an earthquake is defined to be m=log l/s, where i is the intensity of the earthquake (measured by the amplitude of the seismograph wave) and s is the intensity of a “standard” earthquake, which is barely detectable. what is the magnitude of an earthquake that is 1,000 times more intense than a standard earthquake? use a calculator. round your answer to the nearest tenth.

Me. i can't figure out this question. give an explanation too. .