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x + y = 54 (1) ( and let x be the smaller number)
3x - y = 14 (2)
Add (1) to (2):
4x + 0y = 68 > x=17 > (I used eq (1)) > y=37
Ans: 17 is the smaller number
Check: 17+37 = 54 (ok)
3(17)-37 = 51-37 = 14 (ok)