If the ratio is 4:3 divide the larger can by 4 which in a) is 25 then multiply by 3 to get surface area of smaller can which would be 75 square inches.
In part b) do the same so 150 divided by 4 is 37.5 multiplied by 3 is 112.5 cubic inches.
It doesn't matter if it is surface area or volume you still use the same ratio of 4:3
