The roots of polynomial $ p(t) $ are:
$$ \begin{aligned}t_1 &= 0\\[1 em]t_2 &= -\frac{ 30 }{ 49 } \end{aligned} $$Step 1:
Get rid of fractions by multipling equation by $ \color{blue}{ 10 } $.
$$ \begin{aligned} 3t+\frac{49}{10}t^2 & = 0 ~~~ / \cdot \color{blue}{ 10 } \\[1 em] 30t+49t^2 & = 0 \end{aligned} $$Step 2:
Write polynomial in descending order
$$ \begin{aligned} 30t+49t^2 & = 0\\[1 em] 49t^2+30t & = 0 \end{aligned} $$Step 3:
Factor out $ \color{blue}{ t }$ from $ 49t^2+30t $ and solve two separate equations:
$$ \begin{aligned} 49t^2+30t & = 0\\[1 em] \color{blue}{ t }\cdot ( 49t+30 ) & = 0 \\[1 em] \color{blue}{ t = 0} ~~ \text{or} ~~ 49t+30 & = 0 \end{aligned} $$One solution is $ \color{blue}{ t = 0 } $. Use second equation to find the remaining roots.
Step 4:
To find the second zero, solve equation $ 49t+30 = 0 $
$$ \begin{aligned} 49t+30 & = 0 \\[1 em] 49 \cdot t & = -30 \\[1 em] t & = - \frac{ 30 }{ 49 } \end{aligned} $$