To find the tax rate, you would need to find that 8 is 8/82≈.0976, or 9.76% of 82. Then use that to multiply by 123, which would be $12.
Another way is that you realize 82 is 2/3 of 123, so the tax would be 2/3 of what tax for $123 would be. So 8=2/3(x), and x=12.
