Step-by-step explanation:
When we say sum we are referring to addition.
And a number and a variable(letter) can't be added. So the sum of 8 and t can't be added.
The sum of 8 and t is;
8+t
When we talk about product or finding the product of a number we are referring to the number we get after multiplying two or more numbers.
And note that with multiplication, a number and a variable(letter) can be multiplied.
The product of 5 and b is;
5×b=5b
