Answer:
Age of Sheri = 30 and Age of Terry = 50
Explanation:
Let the present age Sheri be s and Terry be t.
We have Sheri’s age in 20 years time will be the same as Terry’s age is now.
That is
s + 20 = t
t - s = 20 ------------------------------eqn 1
Ten years from now, Terry’s age will be twice Sheri’s age
t + 10 = 2s
2s - t = 10 ------------------------------eqn 2
eqn 1 + eqn 2
t - s + 2s - t = 20 + 10
s = 30
Substituting in eqn 1
t - 30 = 20
t = 50
Age of Sheri = 30 and Age of Terry = 50