We are given two equations:

1. The height of the arrow as a function of time: $y = -5t^2 + 18t - 0.25$
2. The height of the target on a hill as a function of the horizontal distance: $y = 0.75x - 1$

To find out when and at what height the arrow strikes the target, we need to set the two equations equal to each other since they represent the same height $y$ when the arrow hits the target. However, we first need to express both equations in terms of the same variable.

Since the first equation is in terms of $t$ (time), and the second one is in terms of $x$ (horizontal distance), we need to relate $x$ to $t$. Assuming the horizontal motion of the arrow has constant velocity (neglecting air resistance), the horizontal distance $x$ can be written as: $x = v_x \cdot t$ where $v_x$ is the horizontal velocity of the arrow.

Unfortunately, the problem does not provide a horizontal velocity $v_x$. Do you have any information on that, or would you like to assume a value for $v_x$, which we can use to proceed?

Alternatively, I can explain how to proceed generally with a variable horizontal velocity and show how the height can be calculated once the velocity is known. Let me know how you'd like to proceed!