Solve primary school math problems? (There should be a tabular flow for application questions)

1, (30-3)/6=27/6=4.5 (km) = 4,500 (m)

2, 16*7 divided by (7-3)=28 (kg)

3、0

4. Lego: 50*4* 1/20= 10 (g)

Milk: 50*4* 19/20= 190 (g)

5、7-5*2/3+2/3

=7-[2/3*(5+ 1)]

=7-4

6. Black: 1500/7=2 14 with 2 remaining. The black balls are arranged first, so the remaining two are white balls.

Black: (1500-2)*3/7=642 (piece)

White: (1500-2)*4/7+2=858 pieces or 1500-642=858 pieces.

7, 15 divided by (5-2)=5.

Length =5*5=25

Width =5*4=20

Height =3*5= 15

Volume =25*20* 15=7500 (square centimeter)