By 7: 20 p. m., only 7 tickets were left. choose the type of error that the sentence contains.

The sentence has an error involving numbers.

Explanation:

By 7: 20 P.M., only 7 tickets were left. is a sentence with a mistake since every time that our writing involves numbers we have to spell the number in letters, therefore the correct sentence should be By 7: 20 P.M., only seven tickets were left. The numbers to express the time are allowed since there are some exceptions where we can use numbers instead of letters.

"facing the rising sun of our new day begun

let us march on till victory is won.",

because the rising sun is a symbol of hope.