Đáp án: $(x,y)\in\{(112, 6), (93, 11), (74, 16), (55, 21), (36, 26), (17,31)\}$
Giải thích các bước giải:
Ta có:
$5x+19y=674$
$\to 19y<674$ vì $x,y\in Z^+$
$\to y\le 35$
Lại có $5x+19y=674$
$\to 5x=674-19y$
Do $5x\quad\vdots\quad 5$
$\to 674-19y\quad\vdots\quad 5$
$\to y$ chia $5$ dư $1$
$\to y=5k+1, k\in Z^+$
Lại có $y\le 35$
$\to 5k+1\le 35$
$\to k\le 6$
$\to k\in\{1,2,3,4,5,6\}$
$\to y\in\{6, 11, 16, 21, 26, 31\}$
$\to x\in\{112, 93, 74, 55, 36, 17\}$
$\to (x,y)\in\{(112, 6), (93, 11), (74, 16), (55, 21), (36, 26), (17,31)\}$
