PLS HELP and explaining would really be appreciated!

What is always true when two whole numbers are subtracted?

Jonathan can throw a baseball 10 1/3 yards. his brother joey can throw a baseball 13 1/2 yards. how much father can joey throw the ball?

Sanderson is having trouble with his assignment. his shown work is as follows: − 3 7 7 3 = − 3 7 × 7 3 = − 21 21 = −1 however, his answer does not match the answer that his teacher gives him. complete the description of sanderson's mistake. find the correct answer.