Answer: Hello there!
if a and b are real numbers:
1) For all real numbers a and b, a+b=b+a: This is true, it is called the commutative property of the addition.
2) For all real numbers a and b, ab=ba: This is true, it is called the commutative property of the multiplication.
3) For all real numbers a and b, a-b=b-a: This is false, a counter example is if we took a = 1 and b = 0; then a -b = 1, and b - a = -1.
4) For all real numbers a and b, a/b=b/a: This is false, if we took a= 4 and b = 2, then a/b = 4/2 = 2, and b/a = 2/4 = 1/2, which are different.
5) For all real numbers a,b, and c, (a+b)+c=a+(b+c): This is true, it is called the distributive property of the addition.
6) For all real numbers a,b, and c, (a-b)-c=a-(b-c): this is false; in the left side of the equation we have (a -b) -c, that if we remove the parenthesis is equal to a -b -c
in the right side we have a -( b - c) if we remove the parenthesis and distribute the minus sign, we get: a -b + c
7) For all real numbers a,b, and c, a(b+c)=ab+ac: This is true, it is called the distributive property of the multiplication.