at first
Ja: u
Jo: 3u

after
Ja: u-68
Jo: 3u-68

3u-68 = 4 x (u-68)
u = 204

Jack's allowance was $204


...

Constant difference question

At first, ratio for $ of Jack : John = 1 : 3
Difference = 3 units - 1 unit = 2 units

After spending $68 each, since Jack's $ is ¼
of John's,

$ of Jack : John = 1 : 4

Difference = 4 units - 1 unit = 3 units

Notice that the difference doesn't change as they each spent the same amount. So we make the units the same

Common multiple of 2 and 3 is 6.


Multiply by 3,

At first, ratio for $ of Jack : John = 3 : 9
Difference = 9 units - 3 units = 6 units

Multiply by 2,
After spending $68 each,

$ of Jack : John = 2 : 8

Difference = 8 units - 2 units = 6 units

So ratio for Jack to John
Before , 3 : 9
After , 2 : 8

9 - 8 = 1
3 - 2 = 1

So they each spent 1 unit. 1 unit = $68

Jack's allowance at first = 3 units
= 3 x $68
= $204