Formula of question

Let the distance travelled in the fist 5 seconds be x metres

We know u=0

When t=5, s=x

When t=10 s=x+150

I am going to use the formula     $${\mathtt{s}} = {\mathtt{ut}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{1}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}{{\mathtt{at}}}^{{\mathtt{2}}}$$

since u=0,  the formula becomes  $${\mathtt{s}} = {\frac{{\mathtt{1}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}{{\mathtt{at}}}^{{\mathtt{2}}}$$

Now we have 2 equations that can be solved simultaneously.

$$\\x=\frac{1}{2}a\times 5^2 \\\\\
x= \frac{1}{2}a\times 25 \qquad (1)\\\\
and\\\\
x+150=\frac{1}{2}a\times 10^2 \\\\
x+150=\frac{1}{2}a\times 100 \\\\
x+150=\frac{1}{2}a\times 25 \times 4 \\\\
\frac{x+150}{4}=\frac{1}{2}a\times 25 \qquad (2)\\\\
$putting these together I get\\\\
\begin{array}{rll}
x&=&\frac{x+150}{4}\\
4x&=&x+150\\
3x&=&150\\
x&=&50\\
\end{array}$$

So the ball rolls 50m in the first 5 seconds   

Is the s after the 5.0 seconds?