We will have the following:
From the problem we construct the expression:
[tex]3x-x^2=-70[/tex]Now, we solve for x:
[tex]\begin{gathered} \Rightarrow-x^2+3x+70=0\Rightarrow-(x^2-3x-70)=0 \\ \\ \Rightarrow-(x+7)(x-10)=0 \\ \\ x=-7 \\ x=10 \end{gathered}[/tex]The number can be either -7 or 10.
