Is it possible for two numbers to have a difference of 8, and a sum of 1?

It depends on the type of numbers that are acceptable. If you state your problem in words

x - y =8

x + y = 1

The answers are    x = 4.5

                           y = -3.5

solution:

→c= a b , that is product of a and b is possible only when when a is m × n matrix and b is n × p matrix.

that is, number of columns of a= number of rows of b.

so, size of matrix , c= a b is , if a = (m × n)matrix

b= (n × p)matrix

then a b = [ (m × n)matrix] ×[   (n × p)matrix ]

→→c= a b= [m × p ] matrix

→→size of product a b will be equal to = number of rows of a × number of columns of b