Calculate the molecular mass of the element
They give:H=1,AI=27,S=32,0=16,Cu=64,P=31,Mg=24,N=14,Na=23

Answer:
Cu3 (PO4)2
3×64 + 2×(31+ 4×16)
192 + 2×(31+64)
192 + 2×(95)
192+190
=382g