7(x+3)
= 7x+ 7*3 (distributive property)
= 7x+ 21.
The final answer is 7x+21~
The person invested $511 at 7%, $803 at 11%, and $ 4500 at 13%,
The third choice is very useful. It's valid because two things that are both equal to 'y' are equal to each other, and it can be easily solved to find 'x'.
The answer is b foo im pretty sure