How many solutions does this linear system have?

Start with the second equation. So start with -15x-3y = 3

Think of -3y as -3( y ). The parenthesis doesn't matter at this point, but will be useful for the next step.

So we have -15x - 3( y ) = 3. We can replace the y with 5x-1 since y = 5x-1 is the first equation

Doing so has us go from this
-15x - 3( y ) = 3
to this
-15x - 3(5x - 1) = 3

After this point, we solve for x like normal
-15x - 3(5x-1) = 3
-15x - 15x+3 = 3
-30x + 3 = 3
-30x + 3 - 3 = 3-3 ... subtract 3 from both sides
-30x = 0
-30x/(-30) = 0/(-30) divide both sides by -30
x = 0

So if x = 0 then y is...
y = 5*x-1
y = 5*0-1
y = 0-1
y = -1

There is only one solution and it is (x,y) = (0,-1)

Choice A

Side Note: this is where the two graphs cross or intersect