Find the area of equilateral triangle whose side 9 cm using heron's formula

pls i am begging to u i need stepbystep calculation

The radius of the base of a cylinder is 10 centimeters, and its height is 20 centimeters. a cone is used to fill the cylinder with water. the radius of the cone's base is 5 centimeters, and its height is 10 centimeters.

X-intercept=-5 y-intercept=2 the equation of the line is

This is so hard and it’s for a test