Question

the sum of the ages of John and Mary is 32. 4 yrs ago, joh was twice as old as Mary. Find the present age of each.

Answer 1

32-4 = 28
28/3 = 9.3
Mary = 9.3+4
= 13.3
= 13 (round to a whole number)
Joh = 9.3x2+4
= 18.6+4
= 22.6
= 23 (round to a whole number)
Therefore Mary is 13 years old and Joh is 23 years old.
Evidence: 23+13-4=32

Answer 2

Make two equations for j = john and m = mary.

j + m = 32

j - 4 = 2m

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Solve for m in the first equation. Subtract j from both sides.

m = 32 - j

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Plug m into the second equation.

j - 4 = 2(32 - j)

Distribute 2 inside the parentheses.

j - 4 = 64 - 2j

Add 4 to both sides.

j = 68 - 2j

Add 2j to both sides.

3j = 68

Divide both sides by 3.

j = 22 2/3

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Plug j into the first equation.

22 2/3 + m = 32

Subtract 22 2/3 from both sides.

m = 9 1/3

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Mary =
`\boxed {9~ 1/3~years~old}`

John =
`\boxed {22~2/3~years~old}`