Answer
The answer is incorrect.
It should be $42$, $R : 24$.
Work Step by Step
$64\times42 + 26 \stackrel{?}{=} 2\,712$
$2\,688 + 26 \stackrel{?}{=} 2\,712$
$2\,714 \neq 2\,712$
However :
$64\times42 + 24 \stackrel{?}{=} 2\,712$
$2\,688 + 24 \stackrel{?}{=} 2\,712$
$2\,712 \stackrel{\checkmark}{=} 2\,712$
