Answer:
[tex]17\ \text{hours and}\ 15\text{ minutes}[/tex]
Step-by-step explanation:
The function is
[tex]-4x+3y=21[/tex]
Where
x = Time in hours
y = Velocity in kilometers per hour
Here y = 30 km/hr
[tex]-4x+3y=21\\\Rightarrow x=\dfrac{3y-21}{4}\\\Rightarrow x=\dfrac{3\times 30-21}{4}\\\Rightarrow x=\dfrac{69}{4}\\\Rightarrow x=17.25\ \text{hours}=17\ \text{hours and}\ 15\text{ minutes}[/tex]
The particle will reach 30 km/hr after [tex]17\ \text{hours and}\ 15\text{ minutes}[/tex].
