3) Mathematical expression would be:
412 - 65 + 0.50x
Where, x = Number of Texts sent
4) Product means result after multiplication, sum after addition, quotient is the result of division with remainder, and difference is how far two numbers are in their magnitude.
"Per" tells us the magnitude for an Unit value.
5) Associative property = (a+b) + c = a+ (b+c)
Commutative property = a + b = b + a
Distributive Property = a(b+c) = ab+bc
They all have their unique characteristics and can be differentiated on that basis.
6) They all are same.
At the end, without parentheses and in proper symbol, it would be equal to -3/4
Hope this helps!