Question

A physicist working in a large laboratory has found that light particles traveling in a particle accelerator increase velocity in a manner that can be described by the linear function −4x + 3y = 21, where x is time and y is velocity in kilometers per hour. Use this function to determine when a certain particle will reach 40km/hr.
The particle will reach 40km/hr when X=_____

Answer 1

24.75 i believe. 

y=4/3x+7
40= 4/3x+7
33=4/3x
24.75 = x

Answer 2

Velocity of particle (y) = 40km/hr Rearrange equation to be 4x = 3y-21 Therefore 4x = 3*40-21 = 99 x = 99/4 = 24.75 hours