A ball is thrown vertically upward with an initial velocity of $150 \mathrm{~m} / \mathrm{s}. The ratio of velocity after 3 \mathrm{~s} and 5 \mathrm{~s} is \frac{x+1}{x}. The value of x is ___________.
\left\{\right. take, \left.g=10 \mathrm{~m} / \mathrm{s}^{2}\right\}