It is given in the question that
Amaya has d dollars in her wallet. Lucy has $12 less than Amaya in her wallet.
Therefore Lucy have
[tex](d-12)[/tex]
in her wallet.
And we have to write an expression to show how much money both girls have altogether in simplest form. And for that, we have to add both total amount in there wallet. That is
[tex]=d+d-12\\= 2d-12[/tex]
And here 2 is common. So we will get
[tex]=2(d-6)[/tex]
