Объяснение:

1)

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

-m+3n=3n-m

3n-m=3n-m

2)

7(2-p)+7p=14

7*2-7p+7p=14

14=14

3)

5a=3(a-4)+2(a+6)

5a=3a-3*4+2a+2*6

5a=3a-12+2a+12

5a=5a

4)

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

4m-3*4+3m+3*3=7m-3

4m-12+3m+9=7m-3

7m-3=7m-3