60 is what percent of 400

Evaluate the expression for the given value of the variable 2×(c2-5) for c=4

Solve x+3y=6 and 4x-6y=6 by elimination . show work !

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: