Y = 3x + 8
8x + 4y = 12

You substitute the given value of y into the equation
8x+4(3x+8)=12
Solve the equation for x
x= -1
Substitute the given value of x into the equation y=3x+8
y=3x (-1)+8
Solve the equation for y
y=5

(x= -1) (y= 5)

Period is the time it takes for one “cycle” to complete. in the parent sine function, period is 2*pi since sin(0) = 0, sin(pi/2) = 1, sin(pi) = 0, sin(3pi/2) = -1, and sin(2pi) = 0. at that point, the sequence repeats itself. i’m not sure if your graph is similar to the sine function since you didn’t provide a picture, but you can find the period by looking at a graph.

There’s no picture i can’t without a picture here