If the rectangle has a fixed width of 300, it means that

where
and
are width and length, respetively.
So given the length
, the are would be

Interest is $1,320. <span><span>P is the principal amount, $6,600.
</span><span>r is the interest rate, 4% per year, or in decimal form, 4/100=0.04.
</span><span>t is the time involved, 5 years time periods.
</span><span>So, t is 5 year time periods.
</span></span>I= p x r x t
In order to get the final number just add $1,320 + $6,600 which is $7,920
C. 10r-3
Because 2r+5=7, the minus 6 and 7 which gives you 1 then minus 4 and 1 witch is 3 then you do 10r-3 and it will get you to 2r+5=7 again. I hope this helped!
Well you can combine like terms. 3x-5=1/4x and that's as far as I got hope this helps. sorry I didn't get all the way through