Solve the following system of equations with the substitution method:

{4x4y=15xy=4\displaystyle {\left\lbrace\begin{array}{ccc} {4}{x}-{4}{y}&=&-{1}\\-{5}{x}-{y}&=&-{4}\end{array}\right.}

Answer: ( , )

Enter your answers as integers or as reduced fractions in the form A/B.