Question

The sum of Sally’s age plus Thomas’s age is 12. The difference of Sally’s age and Thomas’s age is 3. Writeand solve a system f equations to find their ages. Interpret the solution.

Answer 1

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Let
Sally's age = s
Tomas's age = t 

The sum of sally's age plus twice tomas's age is 12
s+2t=12...........(1)
The difference of sally's age and tomas' is 3.
s-t=3
s=3+t.........(2)
Put the value of s from (2) to (1)
s+2t=12...........(1)

3+t+2t=12
3t=12-3
3t=9
t=9/3
t=3
Put the value of t in (2)
s=3+t
s=3+3
s=6 

Sally's age = s = 6
Tomas's age = t = 3