What is the answers to 12, 13, &

1yd 1 ft = 1 1/12 1 1/3 1 1/2 1 1/6

How do you figure out which order to do two step equations in? like which thing do you subtract/add/multiply/divide first? i understand that you do the opposite of whatever's shown on the opposite side, but when?

Which is greater or equal 312 mg or 312 dg