2 câu trả lời
1+...
1 + x + 13 = 100
1 + x = 100 - 13
1 + x = 87
x = 87 - 1
x = 86
1+...+13=100
1+.... =100-13
1+... =87
... =87-1
... =86
=>1+86+13=100
1+...
1 + x + 13 = 100
1 + x = 100 - 13
1 + x = 87
x = 87 - 1
x = 86
1+...+13=100
1+.... =100-13
1+... =87
... =87-1
... =86
=>1+86+13=100
