670*200-52800:40
1) 670* 200 = 134000
2) 52800:40 = 1370
3) 134000-1370 = 132630
657450:90+83*600
1) 657450:90 = 7305
2) 83*600 = 49800
3) 49800+7305 = 57105
(612237-240037):40
1)612237-240037 = 372200
2)372200:40 = 9305
70*(100100-99800)
1)100100-99800 = 300
2)300*70 = 21000