S is the three digit number. h - a number of hundreds t - a number of tens o - a number of ones
S = 100h + 10t + o
The last two digits add to make ten: t + o = 10 The first and last digits add to make eight: h + o = 8 The first two digits add to make twelve: h + t = 12
t + o = 10 ⇒ o = 10 - t h + o = 8 ⇒ o = 8 - h _______ 10 - t = 8 - h h + t = 12 ⇒ h = 12 - t _______ 10 - t = 8 - (12 - t) 10 - t = 8 - 12 + t 10 - t = -4 + t 10 + 4 = t + t 2t = 14 t = 14/2 = 7 ______
