Answer:
Step-by-step explanation:
1,8
5,7
2,3
Given a temperature C in celsius, you can convert it to Fahrenheit by using the formula

In your case C=39, so you have

5x -15 + 3 -8x = 13
5x -12 -8x = 13
5x -8x =13 -12
-3x = 1
x = -1/3
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