solve for x

x/18=21/4

Volume - tennis ball can

A cylindrical can is just big enough to hold three tennis balls. The radius of a tennis ball is 5 cm. What is the volume of air that surrounds the tennis balls? Please explain..

Dimensions/Perimeter

Three buildings are connected together as one. One section is 9'2", another is 45'8" x 16'3" and the last one is 18'9" x 15'8". (The shape is a backward square letter c) What are the dimensions of the courtyard and what is the perimeter of the building? Please explain...

4U- conics problem!!!

This is a conics problem that i have encountered and have problems in solving it....well i have started it but i end up with too four equations and too many variables. However, i didn't solve it in the parametric way so i suspect it could be easier but i do have problems in solving most conics ques via the parametric way. Well here is the question: "The equations of two ellipses are i) 4x (squared) + 9y (squared) = 36 (ii) 2x (squared) + 3y (squared) = 30. A tangent to ellipse (i) meets the ellipse (ii) at the points P and Q. Show that the tangents at P and Q to ellipse (ii) are at right angles to one another. IF it is possible to solve it.please provide with sufficient working that i... click for more

Graph

Graph the linear equation for the indicated values of the independent variable.show this on a Graph as well as the formula V=50n + 30, 0.1<= n <= 0.9