1) 117-63*15:21+428 = 117 +428 - (9*7*3*5):3*7 =545 - 5*9= 545-45=500
2)51+195*18:130-78 = 51+ (5*3*13*6*3):2*5*13 -78= 51+ 54:2-78=51+27-78=78-78=0
3)(2323+3760-14*304):203= (6083-4256):203=1827:203=9
4) (49*104-2891+512):247 =(5096-2891+512):247=(2205+512):247=2717:247=11