С названием формул не могу(
1.
Ar(Cu²O) = 64x2 + 16 = 144
Mr(Cu) = 128/144 = 0.89(89%)
Mr(O) = 1 - 0.89 = 0.11 (11%)
2.
Ar(Na³PO⁴) = 23x3 + 31 + 16x4 = 164
Mr(Na) = 69/164 = 0.42(42%)
Mr(P) = 31/164 = 0.19(19%)
Mr(O) = 1 - 0.42 - 0.19 = 0.39(39%)
3.
Ar(AlCl³) = 27 + 35.5x3 = 133.5(134)
Mr(Al) = 27/134 = 0.2(20%)
Mr(Cl) = 1 - 0.2 = 0.8(80%)
4.
Ar(Ba³N²) = 137x2 + 14x2 = 302
Mr(Ba) = 274/302 = 0.9(90%)
Mr(N) = 1 - 0.9 = 0.1(10%)
5.
Ar(KNO³) = 39 + 14 + 16x3 = 101
Mr(K) = 39/101 = 0.39(39%)
Mr(N) = 14/101 = 0.14(14%)
Mr(O) = 1 - 0.39 - 0.14 = 0.47(47%)
6.
Ar(Fe(OH)²) = 56 + 2(16 + 1) = 90
Mr(Fe) = 56/90 = 0.62(62%)
Mr(O) = 32/90 = 0.36(36%)
Mr(H) = 1 - 0.62 - 0.36 = 0.02(2%)
7.
Ar(Mg(NO³)²) = 24 + 2(14 + 16x3) = 148
Mr(Mg) = 24/148 = 0.16(16%)
Mr(N) = 28/148 = 0.19(19%)
Mr(O) = 1 - 0.16 - 0.19 = 0.65(65%)
8.
Ar(Al²(SO⁴)³) = 27x2 + 3(32 + 16x4) = 342
Mr(Al) = 54/342 = 0.16(16%)
Mr(S) = 96/342 = 0.28(28%)
Mr(O) = 1 - 0.16 - 0.28 = 0.56(56%)
1) 30 : 4 = 7,5 (р.) - снизится цена
2) 30 - 7,5 = 22,5 (р.) - новая цена тетради
3) 850 : 22,5 ≈ 37 (тетр.)