Question

Cho M = -20

M = ( m - b + 11 ) - ( -m - b + 15 ) - m

Answer 1

Ta có : (m-b+11)-(-m-b+15)-m=-20

       => m-b+11+m+b-15-m=-20

       => m+m-m+b-b+11-15=-20

      => m+(-4)=-20

      => m= -20+4

      => m= -16

Chúc bạn học giỏi 

Đừng quên nhé ! ^-^

Answer 2

Vì M= -20

=>-20 = (m-b+11)-(-m-b+15)-m

=> -20=m-b+11+m+b-15-m

=> -(m-b+11+m+b-15-m)=20

=> -m+b-11-m-b+15+m=20

=> -m+b-m-b+m=20+11-15

=> m-m+b-b+m = 16

=> m=16

Vậy m=16