Can someone please help me? :(

Which number should be placed before f2 on the reactants side equation to make equation balanced? xe + > xef4

This is a portion of the earths surface that may be far from tectonic plates boundaries yet experiences volcanism due to a rising mantle plume or some other cause

An isotope undergoes radioactive decay. the new isotope that forms has an atomic number fhat is 2 less than the original isotopes. which kind of decay has occured and how do you know