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