з.1. 54-62=-10

-96:(-10)=9,6

ОТВ.9,6

з.2. 13-69=-56/42

56/42*6/56*7/4=1/4

ОТВ:1/4

з.4 2,1*2.7=5.67

5,67+6,43=12,1

Отв.:12,1

1. -96:(54-62)=-96/-8=12

2. 13-69/42 : 56/6 * 7/4=-1/4

a)13-69/42 : 56/6=  -56/42 * 6/56 = -336/2352 = -1/7 ( дробью )

б)-1/7 * 7/4=-1/4(дробью)

3. x-x/4=99

3x/4=99

3x=99*4

3x=396

x=396/3

x=132

4. 2.1*2.7+6.43=5,67+6,43=12.1