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Answer:
5 years
Step-by-step explanation:
We want to find x such that ...
2(5 +x) = 15 +x . . . . . after x years, Joyce will be 2 times as old
10 +2x = 15 +x . . . . . eliminate parentheses
x = 5 . . . . . . . . . . . subtract x+10
Joyce will be twice as old as Mensah in 5 years.