First, there was $37.50. Then, there was a tax of 8%. Then, there was a tip of 18%. Since the tip is after the tax, it's not going to affect it, and we can essentially ignore it.
The real question here is just <em>what is 8% of $37.50?</em>
To find the percent of something, first you need to put the percent as a decimal.
8% in decimal form is 0.08 (If you think about it literally, they're both 8 hundredths)
Finally, just multiply the percent in decimal form by the number.