Question

Mr. Yi buys vegetables at a market. He purchases 6 pounds of potatoes, p, and 3 pounds of onions, n, for $18. Onions cost twice as much as potatoes. To determine the unit price for each item, his daughter sets up and solves the system of equations shown. 6p + 3n = 18 and 2n = p 6(2n) + 3n = 18 12n + 3n = 18 15n = 18; n = $1.20 Onions cost $1.20 per pound. Analyze the daughter’s solution. Which statements are true? Check all that apply.
The equation 2n = p should be 2p = n.The equation 6p + 3n = 18 should be 
6n + 3p = 18.The actual cost of the onions is $3.00 per pound.Potatoes cost $0.60 per pound.Potatoes cost $1.50 per pound.Potatoes cost $2.40 per pound.

Answer 1

6p + 3n = 18
2p = n

6p + 3(2p) = 18
6p + 6p = 18
12p = 18
p = 18/12 = 1.50

2p = n
2(1.50) = n
3 = n

true statements : The equation 2n = p should be 2p = n
                            The actual cost of onions is $ 3 per lb
                            Potatoes cost $ 1.50 per lb