Ihave a16hp 42 in craftman riding mower when you let out in the clutch to put it in gear the mower dies what is the cause of this?

Make sure that the safety switch under your seat is not faulty. Also, make sure that you have good clean fuel. If not, drain it and fill with fresh gas. Also check to see that there are no obstructions under the deck. Were your blades on when the mower died? If so, it's possible that grass or some other material is restricting the movement of the blades. This can cause it to die.