Answer
$x=50$
Work Step by Step
Add $15x$ and $900$ to both sides of the equation to obtain:
\begin{array}{ccc}
&60x-900+15x+900&=&-15x+2850+15x+900
\\&75x&=&3750\end{array}
Divide 75 on both sides of the equation to obtain:
$x=\dfrac{3750}{75}
\\x=50$
