I don’t understand this problem

Answer:
First we just have to find two components, the slope and a point. The point is given but no slope.
y = 3 is only a horizontal line that passes (0,3). A horizontal line does not have a slope (or the slope is 0).
The line is said to be parallel to it so the slope must also be 0 and just a horizontal line.
So the equation of the line is,
y = mx + b
Substitute the slope and (5,7) to find b.
7 = 0(5) + b
7 = b
The equation of the line would be like this,
y = 0x + 7
y = 7