P should form five covalent bonds. In this strcuture P form three single bond with 3-hydroxyl groups while one single bondformed with oxygen. As oxygen will form two bonds , it carry negative charge, while P should form five bond but here it is forming 4 bonds due to this P has positive charge but overall structure contain neutral charge due to cancellation of positive and negative charges. Beside this, there are 3 H, Four O and One P according to formula H3PO4.
Since one atmosphere is 29.9213 inches of mercury, we can simply find this by taking 29.9213 and multiplying that by 1.24. You end up with 37.102412 inches of mercury. I hope this helps you out, and good luck on the rest of your homework.