The answers you could use are both the second and the forth. But mostly the fourth.
Answer:

Step-by-step explanation:
Here, the given expressions are:
A) 
Solving this, we get

⇒
B) 
Now, solving this, we get

⇒
C) 
Simplifying this, we get

⇒ 
Equation: Y=5x+25
X= 20days
Y=5(20)+25
Y=100+25
Y=125
Answer is 125cards