Hello!
To solve this exercise, we have to calculate the cost of each option. Let's do it:
• £108 for 90 pairs
Let's make a division to calculate the cost of each pair of contact lenses:
[tex]\frac{108}{90}=\pounds1.20\text{ each pair}[/tex]£1.15 for each pair
Let's multiply to obtain the total cost of buying 90 pairs:
[tex]\pounds1.15\cdot90=\pounds103.50[/tex]As we can see, George should use option B because it's cheaper than option A.