(2)=-2.6-3.4+2.3+ 1.5-2.3=-6+2.3+ 1.5-2.3=-3.7+ 1.5-2.3=-2.2-2.3=-4.5

(3)= 13+53-2 1=45

(4)=(-3+2)? +(3- 1)? =- 1+2? =

Eleven (1) Your question should be wrong.

(2)=3/ 17-3.36+7.36+ 14/ 17=(3/ 17+ 14/ 17)+(7.36-3.36)= 1+4=5

(3)

Because: 1+(-2) =- 1, 3+(-4) =- 1, and the combination rate can be used arbitrarily, add two adjacent positive and negative numbers.

So:1+(-2)+3+(-4)+...+99+(-100)

=[ 1+(-2)]+[3+(-4)]+ …… [99+(- 100)]

= - 1+(- 1)+(- 1)+...+(- 1) (50- 1)

=(- 1)×50

=-50

I hope I can help you.