How to add with unlike denominators?

Which addition property is being illustrated below? (type commutative or associative) (6 + 7) + 1 = 6 + (7 + 1)

Which expression will have the same sum as 3_8 + 1/4?

Each cookie sells for $0.50 sam spent $90 on baking supplies and each cookie cost $0.25 to make how many cookies does sam need to sell before making a profit formula: sales> cost