How does the "elastic clause" gives congress authority to take action on other issues unknown to the framers of the constitution? explain.

Well, it gives Congress authority to pass any laws that are "necessary and proper" to carrying out any of the governments expressed powers. Such as levying taxes, declaring war etc. So for any issue that the Framers of the Constitution couldn't predict, Congress can pass a law that allows them to carry out their enumerated powers.

The elastic clause is (Article I, Section 8) granting Congress the power to pass all laws necessary and proper.