It usually takes two people to open a car hood with a broken latch. One person holds down the handle or lever to release the latch, while the other person pushes down on the hood to get it to pop up.
One person may be able open a hood with a broken latch by holding down the lever inside the car with the right hand and, with the car door open, pounding on the hood with the left hand. A rusty latch is often the reason a latch fails. Clean the rust off the latch with a can of carburetor cleaner. Popular Mechanics recommends that you fix a broken latch before the cable breaks, which makes the hood even more difficult to open.