900-6*7-512+49/7 = 6*6/9*3/2= (6+12)/(25-23)+5*8= 750-8*7+104-54/6= 8,3/4*6/9= (14+22)/(21-17)+8*9=

1)900-6*7-512+49/7 = 900-42-512+7=353; 2)6*6/9*3/2=6; 3)(6+12)/(25-23)+5*8=18/2+5*8=49; /// 4) 750-8*7+104-54/6=750-56+104-9=789; 5)8,3/4*6/9=83/10*1/4*2/3=83/40*2/3=83/60=1 23/60; 6) (14+22)/(21-17)+8*9=36/4+72=9+72=81