If a material contains 3 elements joined in a fixed proportion it is an

If a material contains 3 elements joined in a fixed proportion, then the material is an "chemical compound", or simply an "compound".

It can't be a mixture, a suspension, or a solution.

==> None of those combinations ALWAYS consists only of elements.

==> None of those combinations consists of elements that are "joined".

==> None of those combinations consists of elements "in a fixed proportion".

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me