we have
[tex]R=\frac{E}{I}[/tex]
Solve for I means that clear the variable I
Multiply by [tex]I[/tex] both sides
[tex]RI=I\frac{E}{I}[/tex]
[tex]RI=E[/tex]
Divide by [tex]R[/tex] both sides
[tex]RI/R=E/R[/tex]
[tex]I=E/R[/tex]
therefore
the answer is
[tex]I=E/R[/tex]