Ответ:\(80-\mathbf{30}=30+20\);\(72+8=69+\mathbf{11}\);\(\mathbf{20}+13=13+\mathbf{20}\);\(100-35=\mathbf{75}-10\);\(\mathbf{75}+20=100-5\);\(16+\mathbf{24}=\mathbf{24}+16\).