OP already did it - CONGRATS!!
here are the steps 2 get the same ans:
(NH4)2 CO3 has 2x N, 8x H, 1x C and 3x O per molecule
so its molecular mass = 2x14 + 8x1 + 1x12 + 3x16
=28+8+12+48
=96g
of that 96g, 8x1=8g is due to Hydrogen
so by ratio n proportion, 1.00g will have 1x8/96 = 1/12g = 0.083g of H
