1. 3 x 5 x 7 x 2 2. 49 x 8 + 49 x 2 3. 173 x 13 - 173 x 3
= ( 5 x 2 ) x 7 x 5 = 49 x ( 8 + 2 ) = 173 x ( 13 - 3 )
= 10 x 7 x 5 = 49 x 10 = 173 x 10
= 10 x 35 = 490 = 1730
= 350
4. ( 28 x 25 ) : 7 6. 2 x 5 x 17 7 . 2 x 34 x 5
= 700 : 7 = ( 2 x 5 ) x 17 = ( 2 x 5 ) x 34
= 100 = 10 x 17 = 10 x 34
= 170 = 340
8. 2 x 69 x 5 5. 35 x 7 + 35 x 3 9 . 8 x 70 x 25
= ( 2 x 5 ) x 69 = 35 x ( 7 + 3 ) = ( 25 x 8 ) x 70
= 10 x 69 = 35 x 10 = 200 x 70
= 690 = 350 = 14000
II . Tìm x
12.680 : x = 4
x = 12.680 : 4
x = 3170