Ciera added negative forty plus negative twenty-one and got the answe +61. What error did Ciera make?

She found the difference of the numbers instead of the sum.

She changed the sign of the number 40 instead of the number 21.

She chose the incorrect sign for the sum.

She did not make an error: negative forty plus negative twenty-one.

Question

Ciera added negative forty plus negative twenty-one and got the answe +61. What error did Ciera make?

She found the difference of the numbers instead of the sum.

She changed the sign of the number 40 instead of the number 21.

She chose the incorrect sign for the sum.

She did not make an error: negative forty plus negative twenty-one.

anonymous · Answer

This is  simple one, she chose the incorrect sign... a negative plus a negative is a negative.