Answer:
Simon's age is 18.
Explanation:
Let Simons age be s and the age of each twin be t.
s + 2t = 48
s - t = 3
Subtract the second equation from the first:
s - s + 2t - (-t) = 45
2t + t = 45
3t = 45
t = 45/3 = 15.
Now we find Simon's age by plugging t = 15 in the second equation:
s - t = 3
s - 15 = 3
s = 3 + 15 = 18.