HELP PLEASE!!! Why is ROI usually calculated as a percentage instead of a dollar amount?

a. It easily helps you compare investments.
b. Because it does not calculate them over the same period of time.
c. The dollar amount is too exact.
d. Because it does not calculate over the interest rate.

The value of x in this system of equations is 1. 3x + y = 9 y = –4x + 10 substitute the value of y in the first equation: combine like terms: apply the subtraction property of equality: apply the division property of equality: 3x + (–4x + 10) = 9 –x + 10 = 9 –x = –1 x = 1 what is the value of y?