Answer
$w = 3$
Work Step by Step
$13(7^{w}) + 20 = 5(7^{w}) + 2764$
$13(7^{w}) - 5(7^{w}) = 2764 - 20$
$(13-5)(7^{w}) = 2744$
$8(7^{w}) = 2744$
$7^{w} = 343$
$7^{w} = 7^{3}$
$w = 3$
Check:
$13(7^{w}) + 20 \overset{?}{=} 5(7^{w}) + 2764$
$13(7^{3}) + 20 \overset{?}{=} 5(7^{3}) + 2764$
$13(343) + 20 \overset{?}{=} 5(343) + 2764$
$4459 + 20 \overset{?}{=} 1715 + 2764$
$4479 = 4479$