Answer:
![\mathbf{a2b}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/n7bg7yv7mwd1nrhwm9dwiuk56z438t8zne.png)
Explanation:
We can simplify it twice.
1) Simplify at first by the factor outside the parentheses, namely 13. So dividing by 13.
![(a6b-3)13\\\\((a6b-3)13)/(13) \Rightarrow (a6b-3)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/5on7ec7394tc2hiz921txev1o7kxw4bhz2.png)
2) Since 6 and -3 are have as their GCD the number 3 then we can divide them both by 3.
![((a6b))/(3)-(3)/(3)\Rightarrow (a2b)-1\Rightarrow\:a2b-1\Rightarrow a2b=1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/6gxgie23u4ce7oi0ar721tkvykfodwhkkp.png)
3) As the question just asks us the left side of the equation before the equal sign. We can rewrite a2b -1 as a2b=1 then the answer
![\mathbf{a2b}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/n7bg7yv7mwd1nrhwm9dwiuk56z438t8zne.png)