А)(a+900):2,если а=4,40,400,4000,40000
1)(4+900):2=452
2)(40+900):2=470
3)(400+900):2=650
4)(4000+900):2=2450
5)(40000+900):2=20850
г)х:18+100,если х=72,180,360,7200,14400
1)72:18+100=104
2)180:18+100=200
3)360:18+100=120
4)7200:18+100=500
5)14400:18+100=700