Question

White phosphorus, P4, is prepared by fusing

Answer 1

2Ca3(PO4)2 + 6SiO2 + 10C ---> P4 + 6CaSiO3 + 10CO

1 mole of Ca3(PO4)2 = 310g
1 mole of P4 = 124g

according to the reaction:
2*310g Ca3(PO4)2----------------124g P4
x g Ca3(PO4)2 ------------------------ 30g P4
x = 150g Ca3(PO4)2

so, your answer is good