Answer:
C. Luisa is incorrect, it's not 0. It's only zero when you get "x=0" as an answer but the variable x got canceled here. And as 3=3, it is a true statement so it includes all real numbers. If you had gotten 3=8 for example, it would be a fake statement, so then no solution.
And for the second part,
1. No solution
5x+24=5x+25
24=25
It's false
2. One solution
12p-7=-3p+8
15p=15
P=1
3. One solution.
3x+20=5x
20 = 2x
X = 10