How can u simply 3/7 to its lowest terms

Plzz ! if you were constructing a triangular frame, and you had wood in the length of 4 inches, 4 inches, and 7 inches, would it make a triangle? would you be able to create a frame from these pieces of wood? yes or no? = explain your mathematical thinking/show your work:

If the equation of a perpendicular bisector of a triangle is y = 2x + 7, what is the slope of the side that it is bisecting? explain how you know. 

What is the measure of dg? enter your answer in the box.