Can someone please explain how to do this problem:

n(x)=4x+15; n(x)=7

Thanks

You invested $5000 between two accounts paying 4% and 9% annual interest, respectively. if the total interest earned for theyear was $350, how much was invested at each rate? $was invested at 4% andwas invested at 9%.

Which expression is equivalent to sq-80

Ling listed all of the factors of a mystery number: 1,2,4,8,16,32 what is the mystery number?