He is incorrect. The addition and subtraction of vector is defined for all cases when you know the information about the vectors
Step-by-step explanation:
Arithmetically you have to find the x-axis and y-axis component for each vector. In case of adition if the components have the same direction you add then, subtract if they have opposite. Always subtraction of two vectors a and b could be defined as the sum of the a plus -b
The average is 13 to get the answer you add all the numbers together then divide by how many numbers you had (ex) 12+18+13+16+6=65 then you divide by how many numbers you have (ex) 65\5=13
