Gabriel used the expression 2.5x + 2y – 2 to represent his total cost, and 28 – 2.5x – 2y to represent the amount of change he should receive from $30. what was gabriel’s error?

Gabriel subtracts 2 instead of adding 2 hence, the mistake is in the 2nd step and this is determined by using the arithmetic operations.

Given :

The amount of change he should receive from $30 will be:

So, Gabriel subtracts 2 instead of adding 2 hence, the mistake is in the 2nd step.

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He should add 2 in 30 but he subtracted 2 from 30                                                      

Step-by-step explanation:

The total cost :

Now he gave $ 30

So, amount change he received:

=

= --b

=  

While we are given that he should receive :

So, the Gabriel's error was in b

He should add 2 in 30 but he subtracted 2 from 30

In b he applies the property of signs incorrectly

(-) * (-) = (+) but he applied (-) * (-) = (-)

By applying wrong property he got the -2 while we applied the correct property we got +2

So, this was the error .                                                                                                                 

step-by-step explanation: yes