This is LaTeX code:
[latex]
7*5^{2(n+1)}+12*6^{n+1}=7*5^{2n+2}+12*6^{n+1}=5^2*7*5^{2n}+6*12*6^n=25(7*5^{2n}+12*6^n)-19*12*6^n
[/latex]