Answer:
Sorry for the $ sign, I meant that pound sign, my computer doesn't have that sign, sorry. So just bear with me, the math is all the same.
The next one is $45+$22.5 = $67.5 for 100 ml. We can then form ratios:
55:80
67.5:100
We can then divide the first ratio by 80 on both of the sides. So we will get
0.688:1
And do the same with second but for 100
0.675:1
So since we are not counting discount on the 80 ml bottle, the best choice is the 50ml bottle with the discount one.
