Sarah and Michelle bought pizza and lemonade for a party. 
 . Sarah bought 3 pizzas and 2 bottles of lemonade for $31. 
• Michelle bought 2 pizzas and 4 bottles of lemonade for $30. 
 Which of the following systems of equations could be used to find p, the cost of one pizza, and b, the cost of a bottle of lemonade? 
A. p + b = 31 
p + b = 30 
В. Зp + 2b = 30 
2p + 4b = 31 
C. 3p + 2b = 31 
2p + 4b = 30 
D. 5p + 6 = 61 
p + b= 30