Question

1.计算（1）（-2.5）+(-52.6)

Answer 1

（-2.5）+(-52.6)

=-2.5-52.6

=-(2.5+52.6)

=-55.1

(-8)+(+21)+(-12)

=-8+21-12

=21-8-12

=21-(12+8)

=21-20

=1

(+30)+(-17.5)+(-20)+(+17.5)

=30-17.5-20+17.5

=30-20-17.5+17.5

=10-0

=10