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Bryan is 25 years older than James and in 5 years Bryan will be twice as old as James, how old are they now?
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Solution 1. System of two equations in two unknowns
B - J = 25, (1)
B+5 = 2*(J+5). (2)
Express B = J + 25 from (1) and substitute it into (2). You will get
(J+25) + 5 = 2*(J+5), (3)
or
J + 25 + 5 = 2J + 10 ---> 25 + 5 -10 = 2J - J ---> J = 20.
Answer. James is 20 years now. Brian is 20 + 25 = 45 years old now.
Check it yourself by calculating and comparing the ages in 5 years.
Solution 2. One equation in 1 unknown.
Let J be the James' age now.
Then Brian's age now is J + 25.
According to the condition,
(J+25) + 5 = 2*(J+5). (1)
This equation is identical to the equation (3) of the Solution 1 above.
So, the solution is the same: J = 20. James is 20 years old now.
Then Brian is 20 + 25 = 45 years old now.
You have the same answer.
