<span>E=<span><span>cm/</span>r</span></span>
To solve for m, you have to get it by itself on one side of the equal sign.
To do that you have to eliminate c and r and put them at the other side.
r is being divided by m, so you have to do the opposite to get it on the other side, which is multiply. Multiplying r to both sides will remove the division, and give you <span>Er=cm</span><span>. So... B is the answer :)</span>
