Let x represent amount invested in the higher-yielding account.
We have been given that a man puts twice as much in the lower-yielding account because it is less risky. So amount invested in the lower-yielding account would be
.
We are also told that his annual interest is $6600 dollars. We know that annual interest for one year will be principal amount times interest rate.
, where,
I = Amount of interest,
P = Principal amount,
r = Annual interest rate in decimal form,
t = Time in years.
We are told that interest rates are 6% and 10%.


Amount of interest earned from lower-yielding account:
.
Amount of interest earned from higher-yielding account:
.

Let us solve for x.



Therefore, the man invested $30,000 at 10%.
Amount invested in the lower-yielding account would be
.
Therefore, the man invested $60,000 at 6%.
13: multiply the amount by the tax rate (to make a percent a decimal move the decimal point 2 places to the left) and add the original amount and the taxed amount together. For 12 do above but then multiply the total by the tip rate and add together (basically the same as the tax again) :) I hope this helps
given: 
$\therefore Ac=\frac{(2)2}{2}=2$
No solution is the correct answer i think