(1):35x68=(30+5)X(70-2)=30X70-30X2+5X70-5X2=2100-60+350-10=2380(2):68x65=(70-2)X(70-5)=70X70-70X5-2X70+2X5=4900-350-140+10=4420
35x68+68x65=68x(35+65)=68x100=6800