Need with this one question, also try to explain.

The number of revolutions of two pulleys is inversely proportional to their diameters. if a 24-inch diameter pulley making 400 revolutions per minute is belted to an 8-inch diameter pulley, find the number of revolutions per minute of the smaller pulley.

Rose bought a new hat when she was on vacation. the following formula describes the percent sales tax rose paid b=t-c/c

Olga bought a new skirt that cost $20. sales tax is 5%. how much did olga pay, including sales tax? 7.