Explanation:
For every 3 lemons Chrissy buys at a farm stand, the total cost increases by $1.80.
cost or 1 lemon = 1.8/3 = $0.6
It means the constant of proportionality is 0.6
If there are x no of lemons, then the total cost will be given by :
y = 0.6x
Hence, this is the required solution.