How do i find out how many solutions does each system of equations have?

To do that you should put it in slope intercept form and then graph, you should already know how to do this.

If they are the exact same equation then there are infinte soltuions
if they have same slope but different y intercept then there are 0 solutions
if different slope then 1 soltuiosn

basically
if ax+by=c and ex+fy=g, when simplified
1. a=e and b=f and c=g, then infinite solutions
2. a=e and b=f and c≠g, then 0 solutions
3. if a≠e or/and b≠f and/or c≠g then 1 solutions
confusing

a.
3x-y=1 and 3y+3=9x
3x-y=1 and 3=9x-3y
3x-y=1 and 9x-3y=3
3x-y=1 and 3x-y=1
same equtions
infinite solutions

b.
y+4x=7 and -2y-4=8x
y+4x=7 and -4=8x+2y
y+4x=7 and 8x+2y=-4
y+4x=7 and 4x+y=-2
y+4x=7 and y+4x=-2
same slope but differen y int
0 solutions

c.
4y=3x+4 and 8y-6x=8
-3x+4y=4 and 8y-6x=8
4y-3x=4 and 8y-6x=8
4y-3x=4 and 4y-3x=4
same
inifninte soltuions