How can I get the solution?

15.) A particle moves along the x-axis such that its position is x(t) =0.25t* -2.91613 +12.25+2 -22t + 21.6 for Ist $4. v(t) A graph of its velocity is shown to the right. At what time does the particle reach its leftmost position? Where is the particle when it reaches its leftmost position