Answer: He saved $12 per week
Step-by-step explanation:
I am confused you basically solved your own question but here is the explanation.
Isaiah gets $12 per week in his allowance, every two weeks he gets $24, so in twenty weeks he would have save $240. Here is an equation.
2W*10 = $240
W = weeks
2 weeks = $24*10 = $240
I hope this helps in anyway