**1. The problem statement, all variables and given/known data**
Evaluate the iterated integral

https://webwork.csun.edu/webwork2_fi...cc695601b1.png **2. Relevant equations**
Fundamental Theorem of Calculus & Fubini's Theorem

**3. The attempt at a solution**
I have been working on this problem for the last hour and haven't been able to solve it thus far. I integrated the inside of the integral with respect to y from 4 to 3, and then integrated the result from the first integral with respect to x from 2 to 1. In the process, I used substitution to solve the integrals.

The answer I keep on getting is (1/(4(3x+4)^4)) - (1/(4(3x+3)^4)) and solve from x= 2 to 1 which results in a small fractional answer of 7.5674005*10^(-5). But my online program keeps on saying its incorrect.

Can anyone give me a heads up as to where I am going wrong? This is one of the few iterated integrals that is giving me problems right now :(