Numerical Methods: Euler to Runge–Kutta · Hard problem

Apply two steps of the backward Euler method $y_{n+1} = y_n + h\, f(t_{n+1}, y_{n+1})$ with $h = \dfrac{1}{2}$ to the decay problem $y' = -5y$, $y(0) = 1$, to estimate $y(1)$. Express your answer as a common fraction.