1) 6800-1648:8+78*4=6906
1. 1648:8=206
2. 78*4=312
3. 6800-306=6594
4. 6594+312=6906
2) 31100-(4180*3+236*8)=16572
1. 4180*3=12540
2. 236*8=1888
3. 12540+1888=14428
4. 31100-14428=16572
3)5110*6-99:33=30657
1. 5110*6=30660
2. 99:33=3
3. 30660-3=30657
4)8130*5+72:24=40653
1. 8130*5=40650
2. 72:24=3
3. 40650+3=40653