To determine the type of solutions for each system of equations, we need to compare the slopes and y-intercepts of the lines. If the slopes are equal and the y-intercepts are different, the lines are parallel and there is no solution. If the slopes are equal and the y-intercepts are the same, the lines are coincident and there are infinitely many solutions. If the slopes are different, the lines intersect at one point, and there is exactly one solution.
The first system of equations is:
\[
\begin{align_}
y_1 &= 2x - 4 \\
y_2 &= -2x + 4
\end{align_}
\]
The slopes are \(2\) and \(-2\), which are different. Therefore, the lines intersect at one point, indicating there is exactly one solution.
The second system of equations is:
\[
\begin{align_}
y_1 &= 2.5x + 4 \\
y_2 &= \frac{5}{2}x + 4
\end{align_}
\]
The slopes are \(2.5\) and \(\frac{5}{2}\), which are equal. The y-intercepts are both \(4\). Since both the slopes and y-intercepts are the same, the lines are coincident, indicating there are infinitely many solutions.
The third system of equations is:
\[
\begin{align_}
y_1 &= 2x + 4 \\
y_2 &= 2x + 2
\end{align_}
\]
The slopes are both \(2\), but the y-intercepts are \(4\) and \(2\), which are different. Therefore, the lines are parallel and do not intersect, indicating there is no solution.
- For the first system: \(\boxed{\text{One solution}}\)
- For the second system: \(\boxed{\text{Infinitely many solutions}}\)
- For the third system: \(\boxed{\text{No solution}}\)