.
The condition gives you two equations
J + D = 34, (1)
2*(J-5) + 3*(D-5) = 61. (2)
Simplify (2):
2J - 10 + 3D - 15 = 61,
2J + 3D = 61 + 10 + 15,
2J + 3D = 86. (3)
From (1), J = 34-D. Substitute it into (3). You will get the single equation for only one unknown D:
2*(34-D) + 3D = 86, (It is how the Substitution method works).
68 - 2D + 3D = 86 ====> D = 86 - 68 = 18.
Answer. David is 18 years old. James is 34-18 = 16 years old.
Check. 2*(16-5) + 3*(18-5) = 2*11 + 3*13 = 22 + 39 = 61.
Solved. // On the way, you learned on how the Substitution method works.
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There is a bunch of lessons on age word problems
- Age problems and their solutions
- A fresh formulation of a traditional age problem
- Really intricate age word problem
- Selected age word problems from the archive
- Age problems for mental solution
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