Explanation:
Aaron (A)=30 years old currently. (Aaron's son (S)=10 years old currently)
PREMISES
3S+10=2(S+10)
ASSUMPTIONS
Let A=Aaron's “current” age (3S in terms of his son's age)
Let S=Aaron's son's “current” age (S)
CALCULATIONS
3S+10=2(S+10)
3S+10=2S+20
(3S-2S)+10=(2S-2S)+20
S+10=0+20
S+(10–10)=20–10
S+0=10
S=
10 years old
and,
if S=10 years old, then
A=3S (Aaron's “current” age in terms of his son's age)
A=3(10)
A=
30 years old
PROOF
If A=30 years old, then the equations
3S+10=2(S+10)
3(10)+10=2(10)+20
30+10=20+20 and
40=40 establish the roots (zeros) A, S={30 years old, 10 years old} of the mathematical statement 3S+10=2(S+10)