Abc is a right angled triangle at b and d is a point on bc. if ad=18cm , bd=9cm and cd = 4 cm, find ac

What is the answer to this question? i'm a bit stumped. also how do i do it? 5(x - 4) = 2(x + 5)

What is the solution to this system of equations? y= 2x - 3.5 x - 2y = -14

Jayne is studying urban planning and finds that her town is decreasing in population by 3% each year. the population of her town is changing by a constant rate.true or false?