=7.2-3.6+3.6+2.5
=(7.2+2.5)+(-3.6+3.6)
=9.7+0
=9.7
2、(-72)-(-37)-(-22)- 17
=-72+37+22- 17
=(-72+22)+(37- 17)
=-50+20
=-30
3、0-(+3)-|-3.5|-(-4.2)
=0-3-3.5+4.2
=-3-3.5+4.2
=-6.5+4.2
=-2.3
4、 1/2-(- 1/2)-(-3/4)- 1/6
= 1/2+ 1/2+3/4- 1/6
= 1+3/4- 1/6
=7/4- 1/6
=2 1/ 12-2/ 12
= 19/ 12
= 1 and 7/ 12
5、2/3- 1/8-(- 1/3)+(-3/8)
=2/3- 1/8+ 1/3-3/8
=(2/3+ 1/3)-( 1/8+3/8)
= 1- 1/2
= 1/2