[instru]

$xy + 5^x = 29$
$5^y + x = 27$

$5^x + xy = 25 + 4$
$5^y + x = 25 + 2$

$= 5^x + xy = 5^2 + 4$ ...... $^x = ^2$ $xy = 4$
$= 5^y + x = 5^2 + 2$


ดังนั้น x = 2 , y = 2