[tex]xy \times {x}^{2} {y}^{3} [/tex]
the answer is
[tex] {x}^{3} {y}^{4} [/tex]
you must add the exponents when multiplying their coefficients. The
[tex]xy[/tex]
are technically
[tex] {x}^{1} {y}^{1} [/tex]
for which your answer is
[tex] {x}^{3} {y}^{4} [/tex]
