Dave can wash $2$2 cars in $4$4 minutes.
How long would it take for him to wash 1 car?
How long would it take him to wash $20$20 cars?
Neil can walk $7$7 dogs in $49$49 minutes.
Buzz bought $6$6 stamps for $24.
Neil bought $10$10 stamps for $50.
Unitary method continued, consolidation, general expression.