Pls need to know ASAP

Use the elimination method to solve the system of equations -x+5y=-4 and 4x+3y=16

How many sides does a regular polygon have if each exterior angle measures 72a.3b.4c.5d.6

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.