Final answer:
Genesis 3:15 demonstrates God's mercy and promise to fix the sin problem after Adam and Eve's sin.
Step-by-step explanation:
The verse reference that demonstrates God's mercy after Adam and Eve's sin and promises to fix the sin problem is Genesis 3:15. In this verse, God states, "And I will put enmity between you and the woman, and between your offspring and hers; he will crush your head, and you will strike his heel." This verse is often referred to as the protoevangelium, which means the first announcement of the Gospel.