21+1=22

1 + 1 = 2 

nho k cho minh nha

x + 900 = 800 + 150

x + 900 = 950

         x = 950 - 900

         x = 50

k cho tớ nha

x+100=200-300-300+400

x+100=0

x=0-100

x=-100

x + 100 = 200 - 300 - 300 + 400

x + 100 = -100 - 300 + 400

x + 100 = -400 + 400

x + 100 = 400 - 400

x + 100 = 0

          x = 0 - 100

          x = -100

\(x+100=0\)

\(x=-100\)

7+5=12

bằng 21

20 x 195 421 = 3908420

h minh ha