Just multiply the inequality by the variable.
In 10 months Lisa will have paid the same amount as Kelly, but in month 11 she will have paid more.
To solve for m means to get it alone on a side
so..
13 + (-12) - (-5) =
13 - 12 + 5 =
1 + 5
6
We need to know that the diagonal AC is congruent to itself and we also need to know that AD and BC are congruent
Hope this helps :)