Which of the following properties describes the mathematical expression? 7 + 2 = 2 + 7

A. Associative

B. Distributive

C. Identity

D. Commutative

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

In triangle △abc, ∠abc=90°, bh is an altitude. find the missing lengths. ah=4 and hc=1, find bh.

Aclassmate thinks that solving a system by graphing gives an exact answer when the lines appear to cross at a grid point, but only an approximate answer when they don't. explain why this isn't true.