Hmm rate=change in price/change in number of books
see left one notebooks,money 6,1.8 12,3.6 change in money/change iin notebooks=(3.6-1.8)/(12-6)=1.8/6=0.3 rate is 0.3 for left one rate is 30 cetns per notebook
right one number of books,price 3,1.05 6,2.1 change in money/change in notebooks=(2.1-1.05)/(6-3)=1.05/3=0.35 price is 35 cents per 12*35=420 cents=$4.20
the blank on bottom right is $4.20 the rate on the left is $0.30 per notebook the rate on the right is $0.35 per notebooks left one is the better deal
