Помогите "Алгебра" 7
буду благодарна!

1. 5a²-5ax-7a+7x=    

5a(a-x)-7(a+x)=

20(4+3)-7)4-3)=

140-7=133

2. m²-mn-3m+3n=

m(m-n)-3(m+n)=

0.5(0.5-025)-3(0.5+0.25)=

0.125-2.25=1.125

3. a(a+b)-5(a-b)=

6.6(6.6+0.4)-5(6.6-0.4)=

6.6*7-5*6.2=77.2

4. a(a-b)-2(a+b)=

7/20(7/20-15/10)-2(7/20+15/10)=

7/20(7/20-30/20)-2(7/20+30/20)=

7/20*23/20-2*37/20=

-0.4025-(-3.7)=4/1025