(1)(-5)2-16+(-2)2
=5-4+2
=3;
(2)(48-27)÷3
=16-9
=1.
I am very worried because my son ________ most of his spare time ________ playing games on the computer.
A.concentrates;on
B.concentrates;in
C.focuses;to
D.focuses;in
在墙体上安设钢板时要注意:墙的砂浆强度不低于,供放置挂架使用。()
A、砂浆强度的75%
B、砂浆强度的70%
C、1.8Mpa
D、18kgd/cm2