3 min 45 sec = 225 sec
8min 30 sec = 510 sec
If it takes 225 sec to make 3 sandwiches and 3 salads, it should only take 225//3 = 75 sec to make 1 sandwich and 1 salad
So let x be the time [ in seconds] to make 1 sandwhich and y be the time [ in seconds] to make 1 salad....and we have this system
1x + 1y = 75
6x + 8y = 510 multiply the first equation by − 6 and add it to the second
2y = 60 divide both sides by 2
y = 30 sec for a salad
And
1x+ 30 = 75 → x = 45 sec for a sandwich