-2 because in the second equation it is : 2x. If you multiply x in the first equation by -2 it will cancel out 2x in the second equation. -2x cancels out 2x. -2x+2x=0
Interest earned in a month
(1.5/100) * 6000
90
Number of months in 4 years
12*4
48
So the interest earned in 4 years
90*48
4320 dollars
Correct answer is 450 <span>cubic meters</span>.