Start by finding to total amount of the tip:
\(Tip = rate * base\)
\(T=rb\)
\(T=25\%\times$65\)
\(T=0.25\times65\)
\(T=$16.25\)
And then add the two together: $65 + $16.25 = $81.25
You can also do it another way by realizing that in total they payed 125% of what the dinner cost:
\(Total=125\%\timescsot\)
\(T=1.25c\)
\(T=1.25\times65\)
\(T=$81.25\) same as above.
