Question 13.

$5^x - 3^y = 13438 \text{ and } 5^{x-1} + 3^{y+1} = 9686$

$5^x+3^y∗15=9686∗5$

$5^x+3^y∗15=48430$

$16*3^y=34992$

$3^y = 2187$

y = 7

$5^x=13438+2187=15625$

x=6

x+y = 13