Question

1) the sum of 8 and t
3) the product of 5 and b

Answer 1

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