s2948cott

That's enough. Just $79 + $18 = $97.

s2948cott

NO.  $79 + $18 = $97.  $100 - $3 = $97. it is wrong.

s2948cott

Yes, $100 - $3 = $97 was wrong, It is unconvincing.
Please remembrance they are primary school ( grade 2 ) students, what is $3, it is $21 - $18 = $3.
      choose:
      $79 + $18 = $97.
      $100 - ( $21 - $18 ) = $100 - $3 = $97. ( $79 was gone. Why? )
      $100 - $100 + $79 + $18 = 0 + $79 + $18 = $97.
      $100 -  $100 - $79  - $18 = 0  - $79  - $18 =-$97
      And more.

s2948cott

Again. About $100 - $3 = $97.  What is 100? It is 79 + 21. What is 3? It is 21 - 18.
(79 + 21) - (21 - 18) = 100 - 3 = 97. Same is 79 + 21 -21 + 18 = 97.
         If  79 = A, 21= B, 18 = C, 97 = D.
         So ( A + B ) - ( B - C ) = D
                 A + B - B + C = D
                 A       +        C = D
           B , Change to amy number . The D = A + C and any time.
         If  B is 13579246800
          So ( 79 +13579246800) -  ( 13579246800 - 18 ) =13579246879 - 13579246782 = 97
           No ,                79                +                    18                 = 97
           D = A + C . It is any time.

s2948cott

Good heavens! That's enough.That's enough.
Use the ABC------,to talk that $79 + $ 18 = $ 97 is right and 100 - 3 = 97 is wrong.
79 is money { $ }, it is from boss to customer, 18 is moeey ( $ ), it is from boss  to
for goods cost. 100 and 3  are number , not money ( $ ) and can change any  time,
so 100 - 3 = 97 is wrong.
$97 + $3 = $100. What is?