Solve each system of linear equations:
y=2x-3
y-2x=-3
y = 2x - 3 ----- eq (i)
y - 2x = - 3 ----- eq (ii)
DON'T solve eq (ii) for y as she suggests because it makes ABSOLUTELY NO SENSE.
I'm sure no one wants to create extra work for her/himself, and if you still choose to do this, it's additional work you're creating for yourself!
Just substitute 2x - 3 for y in eq (ii) to get: 2x - 3 - 2x = - 3
2x - 2x = - 3 + 3
0 = 0 <===== This equation is TRUE! Therefore, an INFINITE NUMBER of solutions exists for this system.
That's it!!