1)
=(69-2)/69 * 31 =31-62/69=30(7/69)
2)
=(2002+1)/2002 * 1999 =1999+ 1999/2002
3)
=[16.8-2+( 2/7 + 1.5）× 28/25 ] ÷ 4.2
=4-[2-( 2/7 + 1.5）× 28/25 ] ÷ 4.2
=4-[2- 25/14 × 28/25 ] ÷ 4.2
=4-[2-2]÷ 4.2
=4
1)
=(69-2)/69 * 31 =31-62/69=30(7/69)
2)
=(2002+1)/2002 * 1999 =1999+ 1999/2002
3)
=[16.8-2+( 2/7 + 1.5）× 28/25 ] ÷ 4.2
=4-[2-( 2/7 + 1.5）× 28/25 ] ÷ 4.2
=4-[2- 25/14 × 28/25 ] ÷ 4.2
=4-[2-2]÷ 4.2
=4