Final answer:
To find the combined amount Marcus and Emma have left, subtract the amount they spent from the total amount they had.
Step-by-step explanation:
To find the combined amount Marcus and Emma have left, we need to subtract the amount they spent from the total amount they had. Marcus had $1.50 and Emma had $0.75, so the total amount they had is $1.50 + $0.75 = $2.25. They spent $1.00, so the amount they have left is $2.25 - $1.00 = $1.25.