Let's call:
a = price of 1 apple
p = price of 1 peach
The total cost is the price of 1 apple times the number of apples plus the price of 1 peach times the number of peaches, therefore the system can be:

Solve for a in the second equation (you can choose to solve for any of the variables in any of the equations, try to understand what is the best):
a = (4.82 - 5p) / 4
Now, substitute in the first equation:
6 · (4.82 - 5p) / 4 + 9p = 7.86
7.23 - (15/2)p + 9p = 7.86
(3/2)p = 0.63
p = 0.42
Now, substitute this value in the formula found for a:
<span>a = (4.82 - 5·0.42) / 4</span>
= 0.68
Therefore, one apple costs
0.68$ and one peach costs
0.42$.
The number 6 could replace the gap :)
45 Cards
12 friends invited; 1/2 came 12 x 1/2=6
Let x stand for the number of cards each friend received
Armando kept 3
6x = 45-3
6x = 42
__ __
6 6
x = 7
Each friend received 7 cards
I think that it is A, 180..